Question

Question 8

a. Describe the three rays that are used to locate images formed by mirrors.

b. Describe the three rays that are used to locate images formed by lenses.

c. What is the equation used to find the image distance? Identify each variable.

d. An object is located 25.0 cm from a convex mirror. The image distance is –50.0 cm. What is the magnification?

e. Compare nearsightedness and farsightedness with respect to the symptoms and the lenses used to correct them.

Answer 1

a) 1 . The rays which are parallel to the principal axis will pass through the focus after reflection.

2. The rays which are incident on the pole of the mirror get reflected from the pole with angle of reflection same as that of the angle of incidence.

3. The rays which passes through the center of curvature will reflect along the same path.

b) 1. The rays which are parallel to the optic axis will pass through the focus after refraction.

2. The rays that passes through the optic center will not bend

3. The rays that passes through the focus will go parallel to the optic axis after refraction.

c) (1/v) + (1/u) = (1/f)

v - image distance

u - object distance

f - focal length

d) for mirrors magnification is given by

M = - (v/u)

v = -50cm , u = 25 cm

M = -(-50/25) = 2

e) Nearsightedness

• Close objects appear clearly

• Far away objects can not appear clearly

• Image of far away objects will be formed in front of the retina.

• Concave lenses are used so that the image of far away objects will be formed on the retina.

Farsightedness

• Distant objects appear clearly

• Close objects did not appear clearly

•Image of close objects will be formed behind the retina

• Covex lenses are used so that the image of the close objects will be formed on the retina