Checkpoint: mirrors, lenses and slabs

A ray meets a plane mirror at 20° to the normal. What is the angle of reflection?

• 70°
• 20°
• 40°

A concave mirror has a radius of curvature of 30 cm. What is its focal length?

• 60 cm
• 30 cm
• 15 cm

A convex mirror shows a car behind you. What kind of image is it?

• Real, inverted and smaller
• Virtual, upright and smaller
• Virtual, upright and bigger

A ray goes from air into water at a slant. How does it bend?

• Away from the normal
• Towards the normal
• It does not bend

A convex lens has a focal length of 20 cm. What is its power?

• +20 D
• +0.2 D
• +5 D

A ray enters a glass slab along the normal. How far is the leaving ray shifted?

• Not at all
• By about half the thickness
• By the thickness of the slab