(a) A beam of light consisting of two wavelengths $400\text{ nm}$ and $600\text{ nm}$ is used to illuminate a single slit of width $1\text{ mm}$. Find the least distance of the point from the central maximum where the dark fringes due to both wavelengths coincide on the screen placed $1.5\text{ m}$ ...
CBSE CLASS 12 • PHYSICS • CHAPTER 10
Wave Optics
112 distinct questions across 157 board paper set appearances (2022–2026).
Assertion (A) : In Young's double-slit experiment, the fringe width for dark and bright fringes is the same.
Reason (R) : Fringe width is given by $\beta = \frac{\lambda D}{d}$, where symbols have their usual meanings.
In a Young's double-slit experiment, the two slits behave as coherent sources. When coherent light waves superpose over each other they create an interference pattern of successive bright and dark regions due to constructive and destructive interference.
Two slits $2\text{ mm}$ apart are illuminate...
(b) In a Young's double-slit experiment, fringes are obtained on a screen placed at a distance $D$ from the slits. It is observed that if the screen is moved $5\text{ cm}$ towards the slits, the fringe width changes by $0.03\text{ mm}$. If the distance between the slits is $1\text{ mm}$, calculate t...
(a) Find the intensity at a point on the screen in Young's double slit experiment, at which the interfering waves of intensity $I_0$ each, have a path difference of (i) $\frac{\lambda}{3}$, and (ii) $\frac{\lambda}{2}$.
OR
(b) A point source of light in air is kept at a distance of $12\text{ cm}$ ...
State Huygens principle. Using it draw a diagram showing the details of passage of a plane wave from a denser into a rarer medium.
Assertion (A) : In interference and diffraction of light, light energy reduces in one region producing a dark fringe. It increases in another region and produces a bright fringe.
Reason (R) : This happens because energy is not conserved in the phenomena of interference and diffraction.
Assertion (A) : In a Young's double-slit experiment, interference pattern is not observed when two coherent sources are infinitely close to each other. Reason (R) : The fringe width is proportional to the separation between the two sources.
The principle of superposition is used to understand the phenomenon of interference of light waves. The principle states that at a particular point, the resultant displacement produced by a number of waves is the vector sum of the displacements produced by each wave. Light waves from two coherent so...
Two light waves of the same intensity $I_0$ each, having a path difference of $\lambda/4$, emanating from two coherent sources, meet at a point. The resultant intensity at the point will be
(A) Zero
(B) $I_0$
(C) $2 I_0$
(D) $4 I_0$
Vandana performs Young's double slit experiment by using orange, green and red lights successively. If the fringe widths measured in the three cases are $\omega_1$, $\omega_2$ and $\omega_3$ respectively, then which of the following is correct?
(A) $\omega_2 > \omega_1 > \omega_3$
(B) $\omega_1 > \o...
Consider the effect on the angular separation of the fringes in a Young's double slit experiment due to the following operations:
(i) the screen is moved away from the plane of the slits,
(ii) the separation between the two slits is increased till fringes are observed.
Which of the following options...
(a) Draw a labelled ray diagram showing the formation of an image by an astronomical refracting telescope in normal adjustment. Hence, obtain the expression for its magnifying power.
OR
(b) A plane wavefront of light of wavelength '$\lambda$' is incident normally on a narrow slit of width 'a' and a ...
The British physicist Thomas Young explained the interference of light using the principle of superposition of waves. He observed the interference pattern on the screen, in his experimental set-up, known now as Young's double slit experiment. The two slits $S_1$ and $S_2$ were illuminated by light f...
The fringe width in a Young's double slit experiment is $\beta$. If the whole set-up is immersed in a liquid of refractive index '$\mu$', then the new fringe width will be : (i) $\beta$ (ii) $\beta\mu$ (iii) $\frac{\beta}{\mu}$ (iv) $\frac{\beta}{\mu^2}$
(a) State Huygens principle. How did Huygens justify the absence of the backwave on a spherical wavefront ?
OR
(b) In a single-slit diffraction experiment, light of wavelength $\lambda$ illuminates the slit of width 'a'. The diffraction pattern is observed on a screen kept at a distance D from th...
(b) (i) What is the difference between a ray and a wavefront ?
(ii) A plane wave is incident on a reflecting surface. Using Huygens principle, show how it is reflected from the surface. Hence, verify the law of reflection.
(iii) Depict refraction of a plane wave by a convex lens.
A physics teacher wants to demonstrate interference with the help of double slit experiment using a laser beam of $633\text{ nm}$ wavelength. Since the hall is large enough, interference pattern is formed on the wall $5.0\text{ m}$ from the slits. For clear and comfortable view by all the students t...
(ii) A parallel beam of light of wavelength $650 \text{ nm}$ passes through a slit of width $0\cdot 6 \text{ mm}$. The diffraction pattern is obtained on a screen kept $60 \text{ cm}$ away from the slit. Find the distance between first order minima on both sides of the central maximum.
(a) A point object is placed in air at a distance R/3 in front of a convex surface of radius of curvature R, separating air from a medium of refractive index $n$ ($< 4$). Find the nature and position of the image formed.
OR
(b) In Young's double slit experimental set-up, the intensity of the centr...
(a) (i) (1) What are coherent sources ? Why are they necessary for observing a sustained interference pattern ? (2) Lights from two independent sources are not coherent. Explain. (ii) Two slits 0.1 mm apart are arranged 1.20 m from a screen. Light of wavelength 600 nm from a distant source is incide...
(a) Two waves, each of amplitude 'a' and frequency '$\omega$' emanating from two coherent sources of light superpose at a point. If the phase difference between the two waves is $\phi$, obtain an expression for the resultant intensity at that point.
(a) A ray of light is incident on a surface separating air from a denser medium A of refractive index $\mu_1$. It is then made incident on the parallel surface of another medium B of refractive index $\mu_2$ at the same angle of incidence. If the angle of refraction in the two media are $30^{\circ}$...
Consider the diffraction of light by a single slit described in this case study. The first minimum falls at an angle $\theta$ equal to : (A) $\sin^{-1} (0.12)$ (B) $\sin^{-1} (0.225)$ (C) $\sin^{-1} (0.32)$ (D) $\sin^{-1} (0.45)$
(ii) In Young's double slit experiment, find the ratio of intensities at two points on a screen when waves emanating from two slits reaching these points have path differences (i) $\frac{\lambda}{6}$ and (ii) $\frac{\lambda}{12}$.
OR
(b) (i) Differentiate between a wavefront and a ray.
(ii) State Huygen's principle and verify laws of reflection using suitable diagram.
(iii) In Young's double slit experiment, the slits $S_1$ and $S_2$ are $3 \text{ mm}$ apart and the screen is placed $1.0 \text{ m}$ away from the slits. It is ...
(a) (i) A plane light wave propagating from a rarer into a denser medium, is incident at an angle $i$ on the surface separating two media. Using Huygen's principle, draw the refracted wave and hence verify Snell's law of refraction.
(ii) In a Young's double slit experiment, the slits are separated b...
(a) A parallel beam of light of wavelength $600\text{ nm}$ is incident normally on a slit of width $0.2\text{ mm}$. If the resulting diffraction pattern is observed on a screen $1\text{ m}$ away, find the distance of (i) first minimum, and (ii) second maximum, from the central maximum.
In a Young's double slit experiment, the slit separation is $0.8$ mm and the interference pattern is obtained on a screen kept $50$ cm from the plane of the slits $S_1$ and $S_2$. If the first bright fringe is formed $0.4$ mm from the central maximum, the wavelength of light used is
(A) $480$ nm
(B)...
(a) In single slit diffraction, explain why the maxima at $\theta = $n + \frac{1}{2}$ $\frac{\lambda}{a}$$ becomes weaker and weaker as n increases. State two important differences between interference and diffraction pattern.
Assertion (A) : The phase difference between any two points on a wavefront is zero.
Reason (R) : A wavefront is the locus of all those points which are in the same phase.
Light waves from two coherent sources of intensity ratio $1 : 81$ interfere to form a fringe pattern. Calculate the ratio of the intensity at the maxima and at the minima in the interference pattern.
OR (b) (i) What would happen to the interference pattern obtained in Young's double slit experiment when : (I) one slit is closed, (II) the source of yellow light is replaced by blue-light source, (III) width of each slit is decreased, (IV) the separation between two slits is gradually decreased, (V...
What are coherent sources of light ? Why are coherent sources of light required to produce interference of light ? Give an example of interference of light in daily life.
(a) In a single slit diffraction pattern, how is the angular width of central maximum affected when (i) slit width is increased (ii) the distance between the slit and the screen is increased. (iii) light of smaller wavelength is used. Justify your answer. (b) A slit of width $\text{d}$ is illuminate...
In Young's double slit experiment, the central maximum is bright in the interference pattern obtained on a screen. What will happen when :
(a) light waves emitted out of slits $S_1$ and $S_2$ have an initial phase difference of $\pi \text{ radian}$ ?
(b) one of the slits is closed ?
Justify your ans...
State Huygens principle. How did Huygens justify the absence of the backwave on a spherical wavefront ?
In a single-slit diffraction experiment, light of wavelength $\lambda$ illuminates the slit of width 'a'. The diffraction pattern is observed on a screen kept at a distance D from the slits.
(i) Depict variation of intensity in the fringe pattern with the angular position of the fringes.
(ii) How is...
OR
The fringe width in the interference pattern formed on the screen is :
(A) $1\cdot2\text{ mm}$
(B) $0\cdot2\text{ mm}$
(C) $4\cdot2\text{ mm}$
(D) $6\cdot8\text{ mm}$
The fringe width in the interference pattern formed on the screen is :
(A) $1\cdot2\text{ mm}$
(B) $0\cdot2\text{ mm}$
(C) $4\cdot2\text{ mm}$
(D) $6\cdot8\text{ mm}$
(a) The wavelength of light used in this experiment is :
(A) $720\text{ nm}$
(B) $590\text{ nm}$
(C) $480\text{ nm}$
(D) $364\text{ nm}$
OR
(b) The fringe width in the interference pattern formed on the screen is :
(A) $1.2\text{ mm}$
(B) $0.2\text{ mm}$
(C) $4.2\text{ mm}$
(D) $6.8\text{ mm}$
(a) Differentiate between interference and diffraction of light.
Two coherent light waves, each of intensity $I_0$ produce interference pattern on a screen. Find the intensity at a point at which the path difference between them is (i) $\frac{\lambda}{3}$, and (ii) $\frac{\lambda}{4}$.
In an interference pattern, $10$ fringes are obtained over a certain distance from its central maximum with light of wavelength $480\text{ nm}$. The number of fringes obtained over the same distance with light of wavelength $600\text{ nm}$ with be :
(A) $6$
(B) $7$
(C) $8$
(D) $10$
OR
(a) Differentiate between interference and diffraction of light.
Two coherent light waves, each of intensity $I_0$ produce interference pattern on a screen. Find the intensity at a point at which the path difference between them is (i) $\frac{\lambda}{3}$, and (ii) $\frac{\lambda}{4}$.
OR
Differentiate between interference and diffraction of light.
Two coherent light waves, each of intensity $I_0$ produce interference pattern on a screen. Find the intensity at a point at which the path difference between them is (i) $\frac{\lambda}{3}$, and (ii) $\frac{\lambda}{4}$.
Assertion (A): Two light sources emitting waves of similar wavelengths are coherent.
Reason (R): Two light sources emitting waves having zero or constant phase difference are known as coherent sources.
Assertion (A) : In a Young's double-slit experiment, interference pattern is obtained by using yellow light. If yellow light is replaced by red light, the fringe width increases.
Reason (R) : Fringe width is inversely proportional to the distance of the screen from the slits.
(a) Explain the diffraction of light due to a single slit.
(b) Light of wavelength $540\text{ nm}$ is incident on a $0\cdot09\text{ cm}$ wide single slit and forms a diffraction pattern on the screen $1\cdot5\text{ cm}$ away from the slit. Find the width of the central maximum.
A double slit set-up was initially placed in a tank filled with water and the interference pattern was obtained using a laser light. When water is replaced by a transparent liquid of refractive index $n > n_{\text{water}}$, what will be the effect on the following ?
(a) Speed, frequency and waveleng...
A parallel beam of light of wavelength $650\text{ nm}$ passes through a slit of width $0.6\text{ mm}$. The diffraction pattern is obtained on a screen kept $60\text{ cm}$ away from the slit. Find the distance between first order minima on both sides of the central maximum.
In a double slit experiment, the two slits are $1\cdot5 \text{ mm}$ apart. The slits are illuminated by a mixture of lights of wavelengths of $600 \text{ nm}$ and $400 \text{ nm}$ and the interference pattern is observed on a screen $1\cdot5 \text{ m}$ away from the slits. Find the minimum distance ...
(a) Define 'wavefront' of a light wave. A plane wavefront is refracted from a convex lens. Draw the shape of the refracted wavefront.
(b) A plane wave travelling in a medium is incident on a plane surface separating this medium from a rarer medium. Draw a diagram to show refraction of the wave. Henc...
In Young's double slit experiment, the screen is moved $30\text{ cm}$ towards the slits. As a consequence, the fringe width of the pattern changes by $0\cdot09\text{ mm}$. If the slits separation used is $2\text{ mm}$, calculate the wavelength of light used in the experiment.
(a) Write the conditions under which two light waves originating from two coherent sources can interfere each other (i) constructively, and (ii) destructively, in terms of wavelength. Can these be applied for two lights originating from two sodium lamps ? Give reason.
(b) Monochromatic light of gree...
In Young's double slit experiment, the separation between the two slits is $1\cdot 0\text{ mm}$ and the screen is $1\cdot 0\text{ m}$ away from the slits. A beam of light consisting of two wavelengths $500\text{ nm}$ and $600\text{ nm}$ is used to obtain interference fringes. Calculate :
(a) the dis...
(b) In Young's double slit experimental set-up, the intensity of the central maximum is $I_0$. Calculate the intensity at a point where the path difference between two interfering waves is $\lambda/3$.
Using the Huygens' principle, briefly describe reflection of a plane wavefront from a reflecting surface. Hence, prove the laws of reflection.
In a Young's double-slit experiment, the intensity at the central maximum in the interference pattern on the screen is $I_0$. Find the intensity at a point on the screen where the path difference between the interfering waves is $\frac{\lambda}{6}$.
Light of wavelength $640\text{ nm}$ incident on the slits in a Young's double-slit experiment produces an interference pattern of fringe width $7\cdot2\text{ mm}$. Calculate the wavelength of light which will produce a pattern of fringe width $8\cdot1\text{ mm}$.
In a Young's double-slit experiment with monochromatic light of wavelength $600\text{ nm}$, and slit separation of $2\text{ mm}$, fringes are observed on a screen at some distance. Calculate the change in fringe width if the screen is moved towards the slits by $10\text{ cm}$.
In a Young's double-slit experiment with light of wavelength $520\text{ nm}$, the fringe width is $0.52\text{ mm}$. What will be the fringe width if the entire apparatus is immersed in water (refractive index $\frac{4}{3}$)?
(a) (i) (1) What are coherent sources ? Why are they necessary for observing a sustained interference pattern ?\n(2) Lights from two independent sources are not coherent. Explain.\n(ii) Two slits $0.1\text{ mm}$ apart are arranged $1.20\text{ m}$ from a screen. Light of wavelength $600\text{ nm}$ fr...
(a) (i) A thin pencil of length $(f/4)$ is placed coinciding with the principal axis of a mirror of focal length f. The image of the pencil is real and enlarged, just touches the pencil. Calculate the magnification produced by the mirror.
(ii) A ray of light is incident on a refracting face AB of a ...
(a) (i) A thin pencil of length $\frac{f}{4}$ is placed coinciding with the principal axis of a mirror of focal length f. The image of the pencil is real and enlarged, just touches the pencil. Calculate the magnification produced by the mirror. (ii) A ray of light is incident on a refracting face AB...
(b) (i) Light consisting of two wavelengths $600 \text{ nm}$ and $480 \text{ nm}$ is used to obtain interference fringes in a double slit experiment. The screen is placed $1.0 \text{ m}$ away from slits which are $1.0 \text{ mm}$ apart.
(1) Calculate the distance of the third bright fringe on the sc...
Assertion (A) : When two coherent sources in Young's double-slit experiment (YDSE) are infinitely close to each other, interference pattern is observed on a screen.
Reason (R) : The fringe width in YDSE does not depend on separation between the two slits.
Light of wavelength $700\text{ nm}$ is incident normally on a slit of width $0.2\text{ mm}$. Find the angular width of the central maximum on a screen placed at a distance of $1\text{ m}$ from the slit.
(a) (A) In Young's double slit experiment, the two slits are 0.15 mm apart. The slits are illuminated by a monochromatic light and an interference pattern is obtained a screen kept 3.0 m away from the slits. The distance between first and eighth minima is 8.0 cm. Find the wavelength of the light use...
(a) (i) A ray of light passes through a triangular prism. Show graphically, how the angle of deviation varies with the angle of incidence? Hence define the angle of minimum deviation.
(ii) A ray of light is incident normally on a refracting face of a prism of prism angle A and suffers a deviation of...
(i) State Huygens' principle. A plane wave is incident at an angle i on a reflecting surface. Construct the corresponding reflected wavefront. Using this diagram, prove that the angle of reflection is equal to the angle of incidence.
(ii) What are the coherent sources of light? Can two independent sodium lamps act like coherent sources? Explain.
(iii) A beam of light consisting of a known wavelength $520 \text{ nm}$ and an unknown wavelength $\lambda$, used in Young's double slit experiment produces two interference patterns such that the fourth bright fringe of unknown wavelength coincides with the fifth bright fringe of known wavelength. ...
Q18. (I) A beam of light consisting of two wavelengths, $4000\text{ \AA}$ and $6000\text{ \AA}$, is used to obtain interference fringes in a Young's double-slit experiment. What is the least distance from the central maximum where the dark fringe is obtained?
OR
(II) In Young's double-slit experim...
(a) Two waves, each of amplitude 'a' and frequency '$ω$' emanating from two coherent sources of light superpose at a point. If the phase difference between the two waves is $\phi$, obtain an expression for the resultant intensity at that point.
OR
(b) What is the effect on the interference pattern i...
The phase difference between any two points on a wavefront of a wave is :
(A) $\pi$
(B) $\frac{\pi}{2}$
(C) Zero
(D) $\frac{\pi}{6}$
(b) (i) Give reasons for the following : (1) Why is an objective lens of large focal length and large aperture used in a telescope ? (2) Two sodium lamps (independent) cannot emit coherent lights. (3) The resultant intensity at any point on the screen varies between zero and four times the intensity...
OR (b) (i) The displacement of two light waves, each of amplitude 'a' and frequency $\omega$, emanating from two coherent sources of light, are given by $y_1 = a \cos \omega t$ and $y_2 = a \cos (\omega t + \phi)$. $\phi$ is the phase difference between the two waves. These light waves superpose at ...
Write two points of difference between interference and diffraction of light.
(b) (i) The displacement of two light waves, each of amplitude 'a' and frequency $\omega$, emanating from two coherent sources of light, are given by $y_1 = a \cos \omega t$ and $y_2 = a \cos (\omega t + \phi)$. $\phi$ is the phase difference between the two waves. These light waves superpose at a p...
OR (b) Consider the diffraction of light by a single slit described in this case study. The first minimum falls at an angle $\theta$ equal to : (A) $\sin^{-1}(0.12)$ (B) $\sin^{-1}(0.225)$ (C) $\sin^{-1}(0.32)$ (D) $\sin^{-1}(0.45)$
(i) The displacement of two light waves, each of amplitude 'a' and frequency $\omega$, emanating from two coherent sources of light, are given by $y_1 = a \cos \omega t$ and $y_2 = a \cos (\omega t + \phi)$. $\phi$ is the phase difference between the two waves. These light waves superpose at a point...
(i) A plane light wave propagating from a rarer into a denser medium, is incident at an angle i on the surface separating two media. Using Huygen's principle, draw the refracted wave and hence verify Snell's law of refraction. (ii) In a Young's double slit experiment, the slits are separated by 0.30...
In a Young's double-slit experiment in air, the fringe width is found to be $0.44\text{ mm}$. If the entire setup is immersed in water $(n = \frac{4}{3})$, the fringe width will be
(A) $0.88\text{ mm}$
(B) $0.59\text{ mm}$
(C) $0.33\text{ mm}$
(D) $0.44\text{ mm}$
OR (b) How will the fringe width be affected in a Young's double slit experiment with light of wavelength $\lambda$ if: (i) the separation between the slits is reduced to half, keeping the distance of the screen from the slits constant? (ii) the distance of the screen from the slits is reduced to ha...
(a) (i) What are coherent sources of light? Briefly explain how a pair of coherent sources are obtained in a Young's double-slit experiment. Mention the conditions for constructive and destructive interferences in this experiment. (ii) An object is kept $20$ $ ext{cm}$ from a convex mirror of radius...
Diffraction of light : According to rectilinear propagation of light, light travels in a straight line. But Italian scientist Grimaldi discovered that light bends near the edges of the aperture of the obstacles whose size is comparable with the wavelength of light. This phenomenon of bending of ligh...
(a) (i) In which case is diffraction effect more dominant — slit formed by 2 blades or slit formed by two fingers ?
(ii) Yellow light ($\lambda = 6000 ext{ \AA}$) illuminates a single slit of width $1 imes 10^{-4} ext{ m}$. Calculate (i) the distance between two dark lines on either side of central...
(a) (i) In which case is diffraction effect more dominant — slit formed by 2 blades or slit formed by two fingers ? (ii) Yellow light ($\lambda = 6000 \text{ \AA}$) illuminates a single slit of width $1 \times 10^{-4} \text{ m}$. Calculate (i) the distance between two dark lines on either side of ce...
(b) (i) What will be the colour of the central bright fringe in Young's double slit experiment if the monochromatic source is replaced by a source of white light ? Give reason for your answer. (ii) In Young's double slit experiment, the slits are separated by $0.3 \text{ mm}$ and the screen is place...
(a) (i) In which case is diffraction effect more dominant — slit formed by 2 blades or slit formed by two fingers ? (ii) Yellow light ($\lambda = 6000$ Å) illuminates a single slit of width $1 \times 10^{-4}$ m. Calculate (i) the distance between two dark lines on either side of central maximum, in ...
In Young's double-slit experiment, the slit separation is made three times and the distance of the screen from the slits is doubled. The fringe width becomes :
(a) $6\text{ times}$
(b) $\frac{3}{2}\text{ times}$
(c) $\frac{1}{6}\text{ times}$
(d) $\frac{2}{3}\text{ times}$
(a) The intensities of the principal maximum and secondary maxima in a single slit diffraction pattern are not equal. Explain.
OR
(b) In a Young's double-slit experiment, set-up in air, the fringe width is found to be $\beta$. If the entire set-up is immersed in water, how would $\beta$ be affected?...
(a) (i) What is a wavefront ? What is the direction of a beam of light with respect to the wavefront associated with it ?
(ii) State Huygens' principle. Using it, explain the propagation of light.
(iii) State two conditions necessary for light from two sources to be coherent.
OR
(b) (i) Name the fac...
In a Young's double slit experiment, the slit separation is $0.8\text{ mm}$ and the interference pattern is obtained on a screen kept $50\text{ cm}$ from the plane of the slits $S_1$ and $S_2$. If the first bright fringe is formed $0.4\text{ mm}$ from the central maximum, the wavelength of light use...
Using Huygen's principle, for a plane wavefront incident on a plane reflecting surface, draw the reflected wavefront. Hence prove laws of reflection.
In a Young's double slit experiment, the path difference at a certain point on the screen between two interfering waves is $\frac{1}{8}$th of the wavelength. The ratio of intensity at this point to that at the centre of a bright fringe is close to (i) 0.80 (ii) 0.74 (iii) 0.94 (iv) 0.85
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
a) Both A and R are true and R is the correct explanation of A
b) Both A and R are true and R is NOT the correct ex...
A narrow slit is illuminated by a parallel beam of monochromatic light of wavelength $\lambda$ equal to $6000\text{ \AA}$ and the angular width of the central maximum in the resulting diffraction pattern is measured. When the slit is next illuminated by light of wavelength $\lambda'$, the angular wi...
a) Draw the graph showing intensity distribution of fringes with phase angle due to diffraction through a single slit. What is the width of the central maximum in comparison to that of a secondary maximum?
b) A ray $PQ$ is incident normally on the face $AB$ of a
(b) A slit of width $0.6\text{ mm}$ is illuminated by a beam of light consisting of two wavelengths $600\text{ nm}$ and $480\text{ nm}$. The diffraction pattern is observed on a screen $1.0\text{ m}$ from the slit. Find : (i) The distance of the second bright fringe from the central maximum pertaini...
(a) In a Young's double slit experimental set-up, the intensity of the light waves from two coherent sources are in the ratio of 9 : 1. Find the ratio of intensity of bright and dark fringes in the interference pattern. (b) Monochromatic light of wavelength 600 nm is incident from air on a water sur...
OR (b) A plane wavefront is incident on a surface separating two media of refractive indices $n_1$ and $n_2$ ($> n_1$). With the help of a suitable diagram, explain its propagation from the rarer to denser medium. Hence, verify Snell's law.
In Young's double slit experiment, the slit separation is $1 \text{ mm}$ and the screen is $1 \text{ m}$ away from the slits. For a monochromatic light of wavelength $500 \text{ nm}$, find (a) the distance of third minima, and (b) the distance of second maxima, from the central maxima.
(a) C and Si both have the same lattice structure, but C is an insulator while Si is a semiconductor. Justify.
(b) What happens to the fringe pattern if one of the slits in Young's double slit experimental set-up is closed ?
(a) In single slit diffraction, explain why the maxima at $\theta = \left$n + \frac{1}{2}\right$\left$\frac{\lambda}{\text{a}}\right$$ becomes weaker and weaker as $n$ increases. State two important differences between interference and diffraction pattern.
OR
(b) A plane wavefront is incident on a s...
(a) (i) Two independent monochromatic sources of light cannot constitute coherent sources. Explain. (ii) Two waves represented by $y_1 = a_1 \cos \omega t$, and $y_2 = a_2 \cos \omega t$ produce an interference pattern in Young's double slit experiment. If the ratio of intensities at maximum and at ...
(a) (i) Write the wavelength range of the following electromagnetic radiation : Gamma-rays, Microwaves and Ultraviolet rays (ii) Write one use each of the above mentioned radiation. OR (b) (i) State Huygens' principle. How did Huygens explain the absence of secondary wavelets in the backward directi...
When light passes through a narrow aperture or falls on an obstacle of very small dimensions, it bends into the shadow region. The bending of light waves around the corners and edges of the obstacles as well as aperture is called diffraction of light. For prominent diffraction effect, the size of th...
(c) If in a diffraction experiment, the width of the slit is slightly increased, then the central maximum of the diffraction pattern becomes :
(i) broader and brighter.
(ii) broader and fainter.
(iii) narrow and brighter.
(iv) narrow and fainter.
The principle of superposition is an important principle in Physics. It helps us to understand many phenomena, for example interference of sound and light waves. According to this principle, the resultant displacement produced at a point, by a number of waves, is the vector sum of the displacements ...
In Young's double slit experiment, with light of wavelength $\lambda$, the slit separation $d = n\lambda$. If the distance of the screen from the plane of the slits $D = n^3\lambda$, then the fringe width will be :
(i) $\frac{\lambda}{n^2}$
(ii) $\frac{\lambda}{n}$
(iii) $n\lambda$
(iv) $n^2\lambda$
In Young's double slit experiment, the source used produces lights of wavelengths $450\text{ nm}$ and $600\text{ nm}$. On the screen, the third maximum corresponding to $600\text{ nm}$ coincides with $n^{\text{th}}$ maxima corresponding to $450\text{ nm}$, where $n$ equals :
(i) 1
(ii) 2
(iii) 3
(iv...