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What is the Luminous Flux of a Source Emitting Radio Waves? - Physics

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प्रश्न

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

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उत्तर

The luminous flux of a source emitting radio waves will be zero, as the luminosity of radio waves is zero.

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Light Process and Photometry
  या प्रश्नात किंवा उत्तरात काही त्रुटी आहे का?
पाठ 22: Photometry - Short Answers [पृष्ठ ४५३]

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एचसी वर्मा Concepts of Physics Vol. 1 [English] Class 11 and 12
पाठ 22 Photometry
Short Answers | Q 1 | पृष्ठ ४५३

संबंधित प्रश्‍न

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?


The yellow colour has a greater luminous efficiency as compared to the other colours. Can we increase the illuminating power of a white light source by putting a yellow plastic paper around this source?


The one parameter that determines the brightness of a light source sensed by an eye is ____________ .


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, ________ .


As the wavelength is increased from violet to red, the luminosity ____________ .


An electric bulb is hanging over a table at a height of 1 m above it. The illuminance on the table directly below the bulb is 40 lux. The illuminance at a point on the table 1 m away from the first point will be about ___________ .


Light from a point source falls on a screen. If the separation between the source and the screen is increased by 1%, the illuminance will decrease (nearly) by ____________ .


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 _________ .


The intensity produced by a long cylindrical light source at a small distance r from the source is proportional to _________ .


A point source of light moves in a straight line parallel to a plane table. Consider a small portion of the table directly below the line of movement of the source. The illuminance at this portion varies with its distance r from the source as ___________ .


Figure shows a glowing mercury tube. The intensities at point A, B and C are related as __________ .


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


A room is illuminated by an extended source. The illuminance at a particular portion of a wall can be increased by

(a) moving the source

(b) rotating the source

(c) bringing some mirrors in proper positions

(d) changing the colour of the source.


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


A source emits light of wavelengths 555 nm and 600 nm. The radiant flux of the 555 nm part is 40 W and of the 600 nm part is 30 W. The relative luminosity at 600 nm is 0.6. Find (a) the total radiant flux, (b) the total luminous flux, (c) the luminous efficiency.


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?


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?


Light travels through a glass plate of thickness t and having a refractive index μ. If c is the velocity of light in vacuum, the time taken by the light to travel this thickness of glass is ______.


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