A point source is at a depth of 1 m from the water surface. The diameter of the circle of light rays on water surface refracted into the air will be (refractive index of water is $\frac{4}{3}$ )

\frac{3}{\sqrt{7}} m

No worries! We‘ve got your back. Try BYJU‘S free classes today!

\frac{6}{\sqrt{7}} m

Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses

\frac{9}{7} m

No worries! We‘ve got your back. Try BYJU‘S free classes today!

\frac{18}{7} m

No worries! We‘ve got your back. Try BYJU‘S free classes today!

Open in App

Solution

The correct option is B $\frac{6}{\sqrt{7}} m$
A circle of radius R appears on the water surface since no rays go out to the air from water surface outside of the circle, since all of them reflect back due to total internal reflection.
In the total internal reflection phenomenon, $μ s i n r = 1$

Therefore $s i n r = \frac{3}{4}$

From trigonometry, $R = 1$ $\times t a n r =$ $\frac{3}{\sqrt{7}}$

Hence the diameter of the circle is $\frac{6}{\sqrt{7}}$

Suggest Corrections

Similar questions

Q. A point source of light is kept below the surface of water

(n_{w} = 4 / 3)

at a depth of

\sqrt{7} m

. The radius of the circular bright patch of light noticed on the surface of water is ______

m

Q. A point source of light is placed

4

m

below the surface of water of refractive index

\frac{5}{3}

. The minimum diameter of a disc, which should be placed over the source, on the surface of water to cut-off all light coming out of water is:

Q. A point source of light is placed at a depth of h below the surface of water of refractive index

μ

. A floating opaque disc is placed on the surface of water so that light from the source is not visible from the surface. The minimum diameter of the disc is

Refractive index of glass is $\frac{3}{2}$ . A ray of light travelling in glass is incident on glass-water surface at an angle 30° with normal. Will it be able to come out into the water. Refractive index of water = $\frac{4}{3}$ .

Q. A point source of light is placed at the bottom of the water lake. If the area of the illuminated circle on the surface is equal to 3 times the square of the depth of the lake. The refractive index of water is :

Join BYJU'S Learning Program

A point source is at a depth of 1 m from the water surface. The diameter of the circle of light rays on water surface refracted into the air will be (refractive index of water is 43)

A point source is at a depth of 1 m from the water surface. The diameter of the circle of light rays on water surface refracted into the air will be (refractive index of water is $\frac{4}{3}$ )