Question

1. A convex mirror has focal length of 20cm and object with a height of 40 cm is placed 30 cm from the mirror calculate the image distance and height?
2. An object is placed at a distance of 25 cm, 15 cm and 20 cm from a concave mirror of focal length 20cm justify your answer without using mirror formula?​

Answer 1

Since the image is real.

So the distance of image from mirror is v=−40 cm

The distance of image from object is u=−20 cm

We know ,

f

1

=

v

1

+

u

1

=

−40

1

+

−20

1

f=

3

−40

cm

Now the magnification m=−

u

v

=−2

Height of object h=2cm

Height of image h

1

=∣m∣×h=2×2=4cm

Answer 2

$\huge\underline\frak\red{Answer★}$

1.) In the above attachment

2.) Given,

Object distance, u=25cm

Focal length, f=20cm

From mirror formula

$\frac{1}{f} = \frac{1}{v} + \frac{1}{u}$

$\frac{1}{ - 20} = \frac{1}{v} - \frac{1}{25}$

$\frac{1}{v} = - \frac{1}{20} + \frac{1}{25}$

$v = 100cm$

The image will be real, inverted magnified