Question

The length of shadow of a tree, 3 m long, is 2 m. At the same time if the length of the shadow of a tower be 50 m, find the height of the tower.​

Answer 1

Answer:

Correct option is

C

50 cm

In order to obtain image coincident with object, the image of object after refraction from the convex lens must be formed on the center of curvature of the convex mirror.

Distance of image from convex lens after refraction from it can be found by using lens equation:

⇒

v

1

=

u

1

+

f

1

=

−30

1

+

20

1

⇒v=60cm

Thus, image is formed at a distance of 60cm from the lens.

Thus, the convex mirror should be kept at distance 60cm−10cm=50cm from the lens such that the image is formed at its center of curvature.

Answer 2

R.E.F image

Let AC be tree and AB be its shadow.

Given: AB =

3

h ---(1)

then,

In △ABC,

AB

AC

=tanθ

3

h

h

=tanθ

tanθ=

3

1

⇒[θ=30

∘

]

∴ Angle of elevation of sun is 30

∘

NOBITA121✔