Question

A converging mirror forms a real image of height 4 cm of an object of height 1 centimetre placed 20 CM away from the mirror. Calculate the image distance. What is the focal length of the mirror?​

Answer 1

Answer:

Converging mirror means concave mirror.

v = 80 and f = 80/-3

Explanation:

Given: Height of an image(h')= 4cm.

Height of an object (h)= 1cm.

Object distance (u)= -20 cm.

To find: Image distance(v)= ?

Focal length (f)= ?

By the formula of magnification,

m=h'/h

m= 4/1

Therefore m=4.

Also m= -v/u

4= -v/-20

-v= (-20)(4)

Therefore v= 80.

Now by Mirror formula,

1/f = 1/v + 1/u

1/f = 1/80 + 1/-20

1/f = 1+(-4)/80

1/f = -3/80

Therefore, f = 80/-3

I hope you get it.

Answer 2

Answer:

h2 = - 4 cm (real iamge)

h2 = - 4 cm (real iamge)h1 = 1 cm

h2 = - 4 cm (real iamge)h1 = 1 cmu = - 20 cm

h2 = - 4 cm (real iamge)h1 = 1 cmu = - 20 cm(i) v = ?

h2 = - 4 cm (real iamge)h1 = 1 cmu = - 20 cm(i) v = ?m = h2/h1 = - (v/u)

h2 = - 4 cm (real iamge)h1 = 1 cmu = - 20 cm(i) v = ?m = h2/h1 = - (v/u)⇒ -4/1 = -(v/-20)

h2 = - 4 cm (real iamge)h1 = 1 cmu = - 20 cm(i) v = ?m = h2/h1 = - (v/u)⇒ -4/1 = -(v/-20)⇒ v = -80 cm

h2 = - 4 cm (real iamge)h1 = 1 cmu = - 20 cm(i) v = ?m = h2/h1 = - (v/u)⇒ -4/1 = -(v/-20)⇒ v = -80 cmImage forms in front of the concave mirror.

h2 = - 4 cm (real iamge)h1 = 1 cmu = - 20 cm(i) v = ?m = h2/h1 = - (v/u)⇒ -4/1 = -(v/-20)⇒ v = -80 cmImage forms in front of the concave mirror.(ii) f = ?

h2 = - 4 cm (real iamge)h1 = 1 cmu = - 20 cm(i) v = ?m = h2/h1 = - (v/u)⇒ -4/1 = -(v/-20)⇒ v = -80 cmImage forms in front of the concave mirror.(ii) f = ?1/v + 1/u = 1/f

h2 = - 4 cm (real iamge)h1 = 1 cmu = - 20 cm(i) v = ?m = h2/h1 = - (v/u)⇒ -4/1 = -(v/-20)⇒ v = -80 cmImage forms in front of the concave mirror.(ii) f = ?1/v + 1/u = 1/f1/-80 + 1/-20 = 1/f

h2 = - 4 cm (real iamge)h1 = 1 cmu = - 20 cm(i) v = ?m = h2/h1 = - (v/u)⇒ -4/1 = -(v/-20)⇒ v = -80 cmImage forms in front of the concave mirror.(ii) f = ?1/v + 1/u = 1/f1/-80 + 1/-20 = 1/f1/f = - (1/80) – 1/20 = (-1 – 4)/80 = - (5/80)

h2 = - 4 cm (real iamge)h1 = 1 cmu = - 20 cm(i) v = ?m = h2/h1 = - (v/u)⇒ -4/1 = -(v/-20)⇒ v = -80 cmImage forms in front of the concave mirror.(ii) f = ?1/v + 1/u = 1/f1/-80 + 1/-20 = 1/f1/f = - (1/80) – 1/20 = (-1 – 4)/80 = - (5/80)f = - 16 cm