When a concave mirror is placed facing the Sun, the Sun’s rays converge to a point 10 cm from the mirror. Now, if you place a 2 cm long candles flame 20 cm away on the principal axis of the mirror, where would you place a screen to obtain the image of the candle? What would see the size of the image? Draw a ray diagram to justify your answer.

Question

When a concave mirror is placed facing the Sun, the Sun’s rays converge to a point 10 cm from the mirror. Now, if you place a 2 cm long candles flame 20 cm away on the principal axis of the mirror, where would you place a screen to obtain the image of the candle? What would see the size of the image? Draw a ray diagram to justify your answer.

Philoid · Accepted Answer

f = -10 cm [ since rays coming from infinity meet at focus using a concave mirror ]

u = -20 cm

Since candle flame is placed at the centre of curvature [ as object distance is 20 cm which is twice of focal length i.e. center of curvature C ], so the image will be formed at C. So screen will be placed 20 cm from the mirror on the same side of the object. Size of the image will be same as the size of object = 2 cm.