. The image of a candle flame placed at a distance of 36 cm from a spherical lens formed on a screen placed at a distance of 72 cm from the lens

Identify the type of lens and calculate its focal length. If the height of the flame is 2.5 cm, find the height of the image. 


Best Answer

Sol. Object distance, u=-36, Image distance, v= +72

f= ?,            (+ve sign is due to the image formed on the screen, hence it is real) ­

type of lens = ?

 height of the object,  h1 = 2.5 cm,          height of the image, h2 =?

According to lens formula:


i. -ve sign of h2 shows that the image  is inverted.

ii. Thus an inverted, magnified, 5 cm long image is formed on the screen.



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