Optics

The power of a lens is measured in :

• Metres

• Hertz

• Dioptres

• Watts

What type of image is formed by a plane mirror?

• Real and inverted

• Real and erect

• Virtual and inverted

• Virtual and erect

What is the focal length of a lens with a power of +5D?

• 5cm

• 10cm

• 20cm

• 25cm

What kind of lens is used to correct myopia?

• Convex lens

• Plano-convex lens

• Concave lens

• Cylindrical lens

What is the cause of dispersion of light in a prism?

• Equal speed of all colours

• Different speeds of different colours

• Reflection of light

• Uniform bending of light