Exam Qs: Telescopes

Question 1

A student experimented with a converging lens whose focal length was known to be approximately 50 cm. She placed an object and screen a fixed distance of 200 cm apart. With the lens 128 cm from the object, she observed a sharp image on the screen.

Calculate the focal length of the lens.

Answer 1

f = 46 cm

using lens equation ( 1/f = 1/u +1/v)

Question 2

give 2 advantages of using a reflecting telescope rather than a refracting telescope

Answer 2

no chromatic aberration

mirrors can be larger as they can be supported from behind

cheaper to construct

NOT SPHERICAL ABERATION AS THIS CAN STILL OCCUR