Question

You produce an image of the Sun on a screen using a thin lens whose focal length is 27.5 cm. What is the diameter of the image in millimeters? (Take the radius of the Sun to be 6.96 × 108 m and its distance to Earth to be 1.5 × 1011 m.)

Answer 1

radius of the Sun R = 6.96 × 10⁸ m

distance of sun from Earth r = 1.5 × 10¹¹ m

Focal length f = 27.5 cm = 0.275 m

We know R / r = X / f

From this diameter of the image X = f ( R / r)

= (0.275) [( 6.96 × 10⁸ m)/( 1.5 × 10¹¹ m)]

= 1.276 x10 ^-3 m

1.276 mm