  Previous Year Questions

## Ray Optics And Optical Instruments

- Practice Previous Year questions to get a better idea of the CBSE exam.
1
Resolving power of a telescope increases with :
A
increase in focal length of eyepiece
B
increase in focal length of objective
C
increase in aperture of eyepiece
D
increase in aperture of objective
How does the angle of minimum deviation of a glass prism vary, if the incident violet light is replaced by red light? Give reason.
When a biconvex lens of glass having refractive index 1.47 is dipped in a liquid , it acts as a plane sheet of glass. This implies that the liquid must have refractive index:
A
greater than that of the glass
B
less than that of the glass
C
equal to that of the glass
D
less than one
How can we explain the reddish appearance of sun at sunrise or sunset? Why does it not appear red at noon?
A ray incident normally on the refracting face is refracted in the prism made of material of refractive index . Complete the path ray through the prism. From which face will the ray emerge? Justify your answer.
Calculate the radius of curvature of an equi-concave lens of refractive index , when it is kept in a medium of refractive index , to have a power of
An equilateral glass prism has a refractive index in the air. Calculate the angle of minimum deviation of the prism, when kept in a medium of refractive index .
Draw a labelled ray diagram of an image formed by a refracting telescope with final image formed at infinity. Derive an expression for its magnifying power with the final image at infinity.
(a) A giant refracting telescope at an observatory has an objective lens of focal length . If an eyepiece of focal length cm is used, what is the angular magnification of the telescope?
(b) If this telescope is used to view the moon, what is the diameter of the image of the moon formed by the objective lens? The diameter of the moon is , and the radius of lunar orbit is .
Explain the following, giving reasons:
(i) When monochromatic light is incident on a surface separating two media, the reflected and refracted light both have the same frequency as the incident frequency.
(ii) When light travels from a rarer to a denser medium, the speed decreases. Does this decrease in speed imply a reduction in the energy carried by the wave?
(iii) In the wave picture of light, intensity of light is determined by the square of the amplitude of the wave. What determines the intensity in the photon picture of light?
Draw a ray diagram to show the image formation by a combination of two thin convex lenses to contact. Obtain the expression for the power of this combination in terms of the focal lengths of the lenses.
(a) Write the necessary conditions for the phenomenon of total internal reflection to occur.
(b) Write the relation between the refractive index and critical angle for a given pair of optical media.
(a) Draw a ray diagram to show image formation when the concave mirror produces a real, inverted and magnified image of the object.
(b) Obtain the mirror formula and write the expression for the linear magnification.
(c) Explain two advantages of a reflecting telescope over a refracting telescope.
Under what conditions is the phenomenon of total internal reflection of light observed? Obtain the relation between the critical angle of incidence and the refractive index of the medium.