A circular area of radius $1 c m$ is placed $2 m$ away from a point source. The source emits light uniformly in all directions. The source is on the line of the normal from the centre of the area. $2 \times 10^{- 3}$ luminous flux is incident on the area. Find the total flux emitted by the source.

250 l m

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

320 l m

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

285 l m

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

355 l m

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

Open in App

Solution

The correct option is A $320 l m$
We have solid angle,
$Ω = \frac{π r^{2}}{d^{2}} = \frac{3.14 \times (1 \times 10^{- 2})^{2}}{2^{2}} = 7.85 \times 10^{- 5}$ rad
Total Flux , $F = \frac{4 π I}{Ω} = \frac{4 \times 3.14 \times 2 \times 10^{- 3}}{7.85 \times 10^{- 5}} = 320 l m$

Suggest Corrections

Similar questions

Q. A point source emitting uniformly in all directions is placed 0.5 m above a table top. The luminous flux of the source is

500

π

lumen. Find the illumnance at a small surface area of the table top 0.8 m from the source

Q. A point source emitting 628 lumen of luminous flux uniformly in all directions is placed at the origin. Calculate the illuminance on a small area placed at (1.0 m, 0, 0) in such a way that the normal to the area makes an angle of 37° with the X-axis.

A point source emitting 628 lumen of luminous flux uniformly in all directions is placed at the origin. Calculate the illuminance on a small area placed at (1.0 m,0 0) in such a way that the normal to the area makes an angle of $37^{\circ}$ with the X-axis

Q. A source emits

31.4

W

of radiant flux distributed uniformly in all directions. The luminous efficiency is

60 l u m e n / W

. Find the luminous intensity of the source.

Q. A source emits 31.4 W of radiant flux distributed uniformly in all directions. The luminous efficiency is 60 lumen watt⁻¹. What is the luminous intensity of the source?

Join BYJU'S Learning Program

A circular area of radius 1 cm is placed 2 m away from a point source. The source emits light uniformly in all directions. The source is on the line of the normal from the centre of the area. 2×10−3luminous flux is incident on the area. Find the total flux emitted by the source.

The correct option is A 320 lmWe have solid angle, Ω=πr2d2=3.14×(1×10−2)222=7.85×10−5 radTotal Flux , F=4πIΩ=4×3.14×2×10−37.85×10−5=320 lm

A circular area of radius $1 c m$ is placed $2 m$ away from a point source. The source emits light uniformly in all directions. The source is on the line of the normal from the centre of the area. $2 \times 10^{- 3}$ luminous flux is incident on the area. Find the total flux emitted by the source.

The correct option is A $320 l m$
We have solid angle,
$Ω = \frac{π r^{2}}{d^{2}} = \frac{3.14 \times (1 \times 10^{- 2})^{2}}{2^{2}} = 7.85 \times 10^{- 5}$ rad
Total Flux , $F = \frac{4 π I}{Ω} = \frac{4 \times 3.14 \times 2 \times 10^{- 3}}{7.85 \times 10^{- 5}} = 320 l m$