(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 prism ABC at an angle of $45^\circ$. The ray emerges from face AC and the angle of deviation is $15^\circ$. The angle of prism is $30^\circ$. Show that the emergent ray is normal to the face AC from which it emerges out. Find the refraction index of the material of the prism. OR (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 $1.0\text{ nm}$ apart. (1) Calculate the distance of the third bright fringe on the screen from the central maximum for wavelength $600\text{ nm}$. (2) Find the least distance from the central maximum where the bright fringes due to both the wavelengths coincide. (ii) (1) Draw the variation of intensity with angle of diffraction in single slit diffraction pattern. Write the expression for value of angle corresponding to zero intensity locations. (2) In what way diffraction of light waves differs from diffraction of sound waves ?

Year	Paper Code	Set	Position
CBSE 2025	Series 55-2	Set 1	Question 33
CBSE 2025	Series 55-2	Set 2	Question 31
CBSE 2025	Series 55-2	Set 3	Question 32

• Step 1: Stating the fundamental formula / law statement (+1 Mark)
• Step 2: Intermediate mathematical substitution or proof steps (+1 Mark)
• Step 3: Correct final value or conclusion with mandatory SI units (+1 Mark)