Question

The image of a candle flame placed at a distance of 45cm from a spherical lens is formed on a screen placed at a distance of 90cm from the lens. Identify the type of lens and calculate its focal length. If the height of the flame is 2cm,find the height of its image

Answer 1

Answer:

Explanation:

Nature of Spherical lens = Convex

Given :-

u = - 45 cm

v = + 90 cm

h₁ = + 2 cm

Solution :-

Using lens formula, we get

1/f = 1/v - 1/u

⇒ 1/f = 1/90 - 1/- 45

⇒ 1/f = 1/90 + 1/45

⇒ 1/f = 1 + 2/90

⇒ 1/f = 3/90

⇒ 1/f = 1/30

⇒ f = + 30 cm

Again, m = h₂/h₁ = v/u

h₂ = v/u × h₁

⇒ h₂ = 90/- 45 × 2

⇒ h₂ = - 4 cm

Hence, the height of image is - 4 cm. Negative sign indicates that it is formed below the principal axis.

Answer 2

Answer:

Answer:According to the question;

Answer:According to the question;Object distance, u=−45 cm

Answer:According to the question;Object distance, u=−45 cmImage distance, v=90 cm