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Home » A student-focussed the image of a candle flame on a white screen using a convex lens. He noted down the position of the candle screen and the lens as under
A student-focussed the image of a candle flame on a white screen using a convex lens. He noted down the position of the candle screen and the lens as under
CBSE | Class 10 | Light Reflection and Refraction | NCERT | Physics
A student-focussed the image of a candle flame on a white screen using a convex lens. He noted down the position of the candle screen and the lens as under

Position of candle = 12.0 cm

Position of convex lens = 50.0 cm

Position of the screen = 88.0 cm

  1. What is the focal length of the convex lens?
  2. Where will the image be formed if he shifts the candle towards the lens at a position of 31.0 cm?
  3. What will be the nature of the image formed if he further shifts the candle towards the lens?
  4. Draw a ray diagram to show the formation of the image in case (iii) as said above.

Given,

Candle flame position = 12.0cm

Lens position= 50.0 cm

Screen position=88.0 cm

1. u= 50-12

     u= 38 cm.

Image distance, v= 88-50

                             v= 38cm

Focal length =1/v – 1/u

Focal length = 1/f

f= 19cm

2. The distance of the object, u= 50-31

                                                    u= 19 cm

Object distance = focal length

Thus, the image is formed at infinity.

3.  If he shifts the candle further towards the lens, the object comes between F and 0 and the image is virtual, enlarged and erect and is formed on the same side of the lens.

4.

i

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