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25) The image of a candle flame placed at a distance of 40 cm from a spherical lens is formed on a screen placed on the other side odistance of 40 cm from the lens. Identify the type of lens and write its focal length. What will be the nature of the image formeflame is shifted 25 cm towards the lens? Draw a ray diagram to justify your answert ad if the candle

Answer»

Object distance, u = -40cm

Image distance, v = 40 cm

Using lens formula,

1/f=1/v-1/u=1/40-1(-40)

or Focal length,

f=+20cm

The positive sign of focal length shows that it is a convex lens.

Now,

Magnification, m = v/u= 40/(-40)= -1

Thus, the image is real, inverted and same size as object.

If candle flame is shifted 25 cm towards the lens, then

u=-(40-25)=-15cm1/20=1/v-1/(-15)=-60cmm=v/u=-60/-15=4Thus the image will be virtual, erect and enlarged.

what is this nonsense 😠



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