KCL Section 5: Magnification (Waves and photons)

Question 1

m = v/u
What does ‘v’ stand for?
What does ‘u’ stand for?

Answer 1

u = distance from the lens to the object 
v = distance from the lens to the image

Question 2

Find the position, nature and linear magnification of the image produced when an object is placed 30cm from

a) a converging lens of focal length 20cm
b) a diverging lens of focal length -20cm.

Answer 2

Image is 2x the size of the object

Image is 0.4x the size of the object

Question 3

A converging lens of focal length 25cm, with a 4cm object placed 35cm from the lens

Answer 3

v = 87.5 cm
m = 2.5
Image formed is real, enlarged, and inverted

Question 4

A diverging lens of focal length 50cm, with a 20cm object placed 80cm from the lens

Answer 4

v = -30.8 cm
m = 0.38
Image formed is virtual, diminished, and upright

Question 5

A converging lens of focal length 14cm, with a 6cm object placed 8cm from the lens

Answer 5

v = -18.7 cm
m = 2.3
Image formed is virtual, enlarged, and upright

Question 6

A diverging lens of focal length 15cm, with a 9cm object placed 5cm from the lens

Answer 6

v = -3.75 cm
m = 0.75
Image formed is virtual, diminished, and upright