Question

Calculate the focal length of a covex lens if u = 10 cm and v = 5 cm​

Answer 1

Image distance, v=50cm

Object distance u=20cm

Since, the image is virtual it will be formed on the same side of the object.

From lens formula,

f

1

=

v

1

−

u

1

f

1

=

−50

1

−

−20

1

=

100

3

f=

3

100

cm= focal length

Answer 2

Answer:

10/3cm

Explanation:

1/v-1/u=1/f

u is mostly negative

1/f=1/5-1/-10

1/f=3/10

f=10/3cm