A beam of light consisting of red, green and blue colours is incident on a right-angled prism. The refractive index of the material of the prism for the above red, green and blue wavelength are 1.39, 1.44 nd 1.47



The Prism will

• separate the blue colour part from the red and green colours

• separate all the three colours from one another

• not separate the three colours at all

• separate the red colour part from the green and blue colours

A beam of light from a source L is incident normally on a plane mirror fixed at a certain distance x from the source. The beam is reflected back as a spot on a scale placed just above the source L. When the mirror is rotated through a small angle θ, the spot of the light is found to move through a distance y on the scale. The angle θ is given by

• y/2x

• y/x

• 2y/x

• y/x

A biconvex lens has a radius of curvature of magnitude 20 cm. Which one of the following options describes best the image formed on an object of height 2 cm placed 30 cm from the lens?

• Virtual, upright, height = 0.5 cm

• Real, invented, height = 4 cm

• Real, inverted, height = 1 cm

• Virtual, upright, height = 1 cm

B.

Real, invented, height = 4 cm

Here, image is real, inverted, magnified field and height of image is 4 cm

A concave mirror of focal length f₁ is placed at a distance of d from a convex lens of focal length f₂. A beam of light coming from infinity and falling on this convex lens concave mirror combination returns to infinity. The distance d must be equal

• f₁ +f₂

• -f₁ +f₂

• 2f₁+f₂

• -2f₁ +f₂

A conversing beam of rays is incident on a diverging lens. Having passed though the lens the rays intersect at a point 15 cm from the lens on the opposite side. If the lens is removed the point where the rays meets will moves 5 cm closer to the lens. The focal length of the lens is 

• -10 cm

• 20 cm

• -30 cm

• 5 cm