Question

When a concave mirror is placed facing the sun the sun rays converse point 10cm from the mirror .Now,if you place a 2cm long candles flame 20cm 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

Answer 1

1 The rays coming from sun i.e., from infinity
Therefore the rays converge at F
F=-10cm
2 position of object is at c
Size of image is same size Therefore the radius c=-20cm

Answer 2

Answer:

v = - 20

$\display \text{h _i = -2 cm}$

Explanation:

Given :

Focal length = 10 cm

Object distance = 20 cm

We have image formula :

1 / f = 1 / v + 1 / u

1 / v = 1 / - 10 + 1 / 20

1 / v = - 1  20

v = - 20.

Therefore , screen would be placed at distance of 20 cm to get image.

We have :

m = - v / u = h_i / h_o

- 20 / 20 = h_i / 2

h_i = - 2 cm.

Hence size of the image is 2 cm.