Ray optics

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° and the prism is made of a material of refractive index 1.5, the angle of incidence is

• 7.5 $\degree$

• $5\degree$

• 15 $\degree$

• 2.5 $\degree$

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

• blue

• green

• violet

• 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

• moves away from the lens with an uniform speed 5 m/s.

• moves away from the lens with an uniform accleration.

• moves away from the lens with a non-uniform acceleration.

• moves towards the lens with a non-uniform acceleration

A passenger in an aeroplane shall

• never see a rainbow.

• may see a primary and a secondary rainbow as concentric circles.

• may see a primary and a secondary rainbow as concentric arcs

• 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 90°. 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 beam of red light would undergo total internal reflection

• The beam of red light would bend towards normal while it gets

  refracted through the second medium.

• The beam of blue light would undergo total internal reflection.

• The beam of green light would bend away from the normal as it

  gets refracted through the second medium.

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 be 1.5, it wil

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

  side.

• act as a concave lens for the objects that lie on its curved side.

• act as a convex lens irrespective of the side on which the object

  lies.

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

The phenomena involved in the reflection of radiowaves by

ionosphere is similar to

• reflection of light by a plane mirror

• total internal reflection of light in air during a mirage.

• dispersion of light by water molecules during the formation of a

  rainbow.

• scattering of light by the particles of air.

The optical density of turpentine is higher than that of water while its mass density is lower. Fig 9.2. shows a layer of turpentine floating over water in a container. For which one of the four rays incident on turpentine in Fig 9.2, the path shown is correct?

• 1

• 2

• 3

• 4

A car is moving with at a constant speed of 60 km h–1 on a straight road. Looking at the rear view 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 s till the other car overtakes. If the two cars

were maintaining their speeds, which of the following statement (s) is/are correct?

• The speed of the car in the rear is 65 km h^-1

• In the side mirror the car in the rear would appear to approach

  with a speed of 5 km h^-1 to the driver of the leading car.

• In the rear view mirror the speed of the approaching car would

  appear to decrease as the distance between the cars decreases.

• In the side mirror, the speed of the approaching car would

  appear to increase as the distance between the cars decreases

Consider an extended object immersed in water contained in a plane trough. When seen from close to the edge of the trough the object looks distorted because

• the apparent depth of the points close to the edge are nearer

  the surface of the water compared to the points away from the

  edge.

• the angle subtended by the image of the object at the eye is

  smaller than the actual angle subtended by the object in air.

• some of the points of the object far away from the edge may

  not be visible because of total internal reflection.

• water in a trough acts as a lens and magnifies the object