Light - part I

An object is placed in front of a convex mirror. Its image is formed

• at a distance equal to the object distance in front of the mirror.

• at twice the distance of the object in front of the mirror

• at twice the distance of the object in front of the mirror

• behind the mirror and it’s position varies according to the object distance

An object at a distance of +15 cm is slowly moved towards the pole of a convex mirror. The image will get

• shortened and real

• enlarged and real

• enlarged and virtual

• diminished and virtual

The angle of incidence i and refraction r are equal in a transparent slab when the value of i is

• 0

• 45

• 90

• depends on the material of the slab

The refractive index of transparent medium is greater than one because

• Speed of light in vacuum< speed of light in transparent medium

• Speed of light in vacuum > speed of light in transparent medium

• Speed of light in vacuum = speed of light in transparent medium

• Frequency of light wave changes when it moves from rarer to denser medium

You are given three media A, B and C of refractive index 1.33, 1.65 and 1.46. The medium in which light will travel fastest is

• A

• B

• C

• equal in all media

As light travels from a rarer to a denser medium, it will have

• increased velocity

• decreased velocity

• decreased wavelength

• both b & c

If a man's face is 25 cm in front of a concave shaving mirror producing erect image 1.5 times the size of face, focal length of the mirror would be

• 75 cm

• 25 cm

• 15 cm

• 60 cm

The image formed by concave mirror is real, inverted and of the same size as that of the object. The position of object should be at

• at the focus

• at the centre of curvature

• between focus and centre of curvature

• beyond centre of curvature

A concave mirror of focal length 20 cm forms an image having twice the size of the object. For the virtual position of the object, the position of object will be at

• 25 cm

• 40 cm

• 10 cm

• infinity

     A student determines the focal length of a device X , by focusing the image of a far off object on the screen positioned as shown in figure The device X is a

• Convex lens

• Concave lens

• Convex mirror

• Concave mirror