Chapter 9: Ray Optics and Optical Instruments

A ray of light incident at an angle θ on a refracting face of a prism emerges from the other face normally. If the angle of the prism is 5^o and the prism is made of a material of refractive index 1.5, the angle of incidence is

a) 7.5^o

b) 5^o

c) 15^o

d) 2.5^o

A short pulse of white light is incident from air to a glass slab at normal incidence. After travelling through the slab, the first colour to emerge is

a) blue

b) green

c) violet

d) red

An object approaches a convergent lens from the left of the lens with a uniform speed 5 m/s and stops at the focus. The image

a) moves away from the lens with a uniform speed 5 m/s

b) moves away from the lens with a uniform acceleration

c) moves away from the lens with a non-uniform acceleration

d) moves towards the lens with a non-uniform acceleration

A passenger in an aeroplane shall

a) never see a rainbow

b) may see a primary and a secondary rainbow as concentric circles

c) may see a primary and a secondary rainbow as concentric arcs

d) shall never see a secondary rainbow

You are given four sources of light, each one providing a light of a single colour- red, blue, green, and yellow. Suppose the angle of refraction for a beam of yellow light corresponding to a particular angle of incidence at the interface of two media is 90o. Which of the following statements is correct if the source of yellow light is replaced with that of other lights without changing the angle of incidence?

The radius of curvature of the curved surface of a plano-convex lens is 20 cm. If the refractive index of the material of the lens is 1.5, it will

a) act as a convex lens only for the objects that lie on its curved side

b) act as a concave lens only for the objects that lie on its curved side

c) act as a convex lens irrespective of the side on which the object lies

d) act as a concave lens irrespective of the side on which the object lies

The phenomena involved in the reflection of radiowaves by ionosphere is similar to

a) reflection of light by a plane mirror

b) total internal reflection of light in the air during a mirage

c) dispersion of light by water molecules during the formation of a rainbow

d) scattering of light by the particles of air

The direction of a ray of light incident on a concave mirror as shown by PQ, while directions in which the ray would travel after reflection is shown by four rays marked 1, 2, 3, and 4. Which of the four rays correctly shows the direction of the reflected ray?

The optical density of turpentine is higher than that of water, while its mass density is lower. The figure shows a layer of turpentine floating over water in a container. For which one of the four rays incident on turpentine in the figure, the path shown is correct?

A car is moving at a constant speed of 60 km h–1 on a straight road. Looking at the rearview mirror, the driver finds that the car following him is at a distance of 100 m and is approaching with a speed of 5 km h –1. In order to keep track of the car in the rear, the driver begins to glance alternatively at the rear and side mirror of his car after every 2 still the other car overtakes. If the two cars were maintaining their speeds, which of the following statement (s) is/are correct?