Question

During an experiment of formation of image using cocave mirror.position of mirror =10cm, position of candle =50cm and position of screen =90cm. Find the focal length of mirror and draw the ray diagram using these distance by assuming suitable scale​

Answer 1

Answer:

Given:

During an experiment of formation of image using concave mirror

Position of mirror = 10 cm

Position of candle =50 cm

Position of screen=90 cm

To find:

Focal length of mirror.

Calculation:

Object distance = 50 - 10 = 40 cm.

Image distance = 90 - 10 = 80 cm.

Since , the images formed on the same site as that of the object , the sign of image distance will also be same as that of object distance (i.e. both will be negative).

Applying Mirror Formula:

\therefore \: \dfrac{1}{f} = \dfrac{1}{v} + \dfrac{1}{u}∴

f

1

=

v

1

+

u

1

= > \: \dfrac{1}{f} = \dfrac{1}{( - 80)} + \dfrac{1}{( - 40)}=>

f

1

=

(−80)

1

+

(−40)

1

= > \: \dfrac{1}{f} = - \dfrac{1}{80} - \dfrac{1}{ 40}=>

f

1

=−

80

1

−

40

1

= > \: \dfrac{1}{f} = \dfrac{ - 1 - 2}{80}=>

f

1

=

80

−1−2

= > \: \dfrac{1}{f} = \dfrac{ - 3}{80}=>

f

1

=

80

−3

= > f = - 26.67 \: cm=>f=−26.67cm

So, focal length of mirror is 26.67 cm

Refer to attached diagram.

Explanation:

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