Question

An object is placed 60cm from concave
lens.the image is formed at a distance
20cm from the optical center.find the
focal length of the lens.is the lens
converging or diverging​

Answer 1

Answer:

The focal length of the concave lens is -30 cm.

Explanation:

The distance of the image from the lens, v = -20 cm

The distance of the object from the lens, u = -60 cm

The focal length of the lens can be found using the lens formula.

 1/f = 1/v - 1/u

⇒ f = uv / (u - v)

   f = (-60 × -20) / (-60 - -20)

   f = 1200 / -40

   f = -30 cm

Concave lenses are diverging lens.