English
Karnataka Board PUCPUC Science Class 11

A Source Emits 45 Joules of Energy in 15 S. What is the Radiant Flux of the Source? - Physics

Advertisements
Advertisements

Question

A source emits 45 joules of energy in 15 s. What is the radiant flux of the source?

Sum
Advertisements

Solution

Given,

Total energy emitted (E) = 45 J

Time (t) = 15 s

Radiant flux of the source is given by,

`"Radiant Flux"="Total energy emitted"/"Time"`

`=45/15=3"W"`

So, the radiant flux of the source is 3 W.

shaalaa.com
Light Process and Photometry
  Is there an error in this question or solution?
Chapter 22: Photometry - Exercise [Page 455]

APPEARS IN

HC Verma Concepts of Physics Vol. 1 [English] Class 11 and 12
Chapter 22 Photometry
Exercise | Q 1 | Page 455

RELATED QUESTIONS

What is the luminous flux of a source emitting radio waves?


The luminous flux of a 1 W sodium vapour lamp is more than that of a 10 kW source of ultraviolet radiation. Comment.


The sun is less bright at morning and evening as compared to at noon although its distance from the observer is almost the same Why?


Three light sources A, B and C emit equal amount of radiant energy per unit time. The wavelengths emitted by the three source are 450 nm, 555 nm and 700 nm respectively. The brightness sensed by an eye for the sources are XA, XB and XC respectively. Then, ________ .


A battery-operated torch is adjusted to send an almost parallel beam of light. It produces an illuminancle of 40 lux when the light falls on a wall 2 m away. The illuminance produced when it falls on a wall 4 m away is close to _________ .


A photographic plate placed a distance of 5 cm from a weak point source is exposed for 3 s. If the plate is kept at a distance of 10 cm from the source, the time needed for the same exposure is _____________ .


A photographic plate is placed directly in front of a small diffused source in the shape of a circular disc. It takes 12s to get a good exposure. If the source is rotated by 60° about one of its diameter, the time needed to get the same exposure will be ___________ .


The brightness-producing capacity of a source

(a) does not depend on its power

(b) does not depend on the wavelength emitted

(c) depends on its power

(d) depends on the wavelength emitted


Mark the correct options.

(a) The luminous efficiency of a monochromatic source is always greater than that of a white light source of same power.

(b) The luminous efficiency of a monochromatic source of wavelength 555 nm is always greater than that of a white light source of same power.

(c) The illuminating power of a monochromatic source of wavelength 555 nm is always greater than that of a white light source of same power.

(d) The illuminating power of a monochromatic source is always greater than that of a white light source of same power.


Mark out the correct options.

(a) Luminous flux and radiant flux have same dimensions.

(b) Luminous flux and luminous intensity have same dimensions.

(c) Radiant flux and power have same dimensions.

(d) Relative luminosity is a dimensionless quantity.


Using figure, find the relative luminosity of wavelength (a) 480 nm, (b) 520 nm (c) 580 nm and (d) 600 nm.


The relative luminosity of wavelength 600 nm is 0.6. Find the radiant flux of 600 nm needed to produce the same brightness sensation as produced by 120 W of radiant flux at 555 nm.


The luminous flux of a monochromatic source of 1 W is 450 lumen watt−1. Find the relative luminosity at the wavelength emitted.


The illuminance of  a small area changes from 900 lumen m−2 to 400 lumen m−2 when it is shifted along its normal by 10 cm. Assuming that it is illuminated by a point source placed on the normal, find the distance between the source and the area in the original position.


Light from a point source falls on a small area placed perpendicular to the incident light. If the area is rotated about the incident light by an angle of 60°, by what fraction will the illuminance change?


An electric lamp and a candle produce equal illuminance at a photometer screen when they are placed at 80 cm and 20 cm from the screen respectively. The lamp is now covered with a thin paper which transmits 49% of the luminous flux. By what distance should the lamp be moved to balance the intensities at the screen again?


Two light sources of intensities 8 cd and 12 cd are placed on the same side of a photometer screen at a distance of 40 cm from it. Where should a 80 cd source be placed to balance the illuminance?


Photo diodes are used to detect ______.


Share
Notifications

Englishहिंदीमराठी


      Forgot password?
Use app×