Geometrical Optics

The diverging lens is

• Thicker in centre and thinner at ends

• Thicker at ends and thinner at center

• Thick at both center

• Thin at both center

If an object is place between F and 2F of a convex lens, the image will be

• Real, inverted and magnified

• Real, erect and magnified

• Virtual, erect and diminished

• Virtual, erect and magnified

The far point for normal eye is

• 25 cm

• 25 m

• 50 m

• Infinity

In compound microscope the focal length of

• Objective is greater that eyepiece

• Eyepiece is greater that objective

• Both are of equal focal lengths

• Lenses of any focal lengths can be used

Two convex lenses of focal lengths 0.3 m and 0.05 m are used to make a astronomical telescope. The distance kept between them is equal to

• 0.35 m

• 0.25 m

• 0.175 m

• 0.15 m

Length of a Galilean telescope in normal adjustment in terms of the focal length of the objective (f₀) and that of the eye piece (f₀) is

• f₀/ f_e

• f_e- f₀

• f₀ - f_e

• f₀ + f_e

The length of a telescope is 100 cm and magnification is 9. The focal lengths of the objective and the eye piece are respectively nearly

• 90 cm and 10 cm

• 85 cm and 15 cm

• 80 cm and 20 cm

• 95 cm and 5 cm

In hot day white clothes are worn because they are good

• Absorbers

• emitters

• reflectors

• none of these

The unit of power of a lens is

• Newton

• Watt

• Horse power

• Diopter

If the focal length of one lens is – 40 cm and that of the other is + 20 cm, the focal length of the combination will be

• 80 cm

• 40 cm

• 30 cm

• 35 cm