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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

Light is incident normally on a small plane surface. If the surface is rotated by an angle of 30° about the incident light, does the illuminance of the surface increase, decreases or remain same? Does your answer change if the light did not fall normally on the surface?


Why is the luminous efficiency small for a filament bulb as compared to a mercury vapour lamp?


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, ________ .


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 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 _____________ .


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.


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


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.


A point source emitting light uniformly in all directions is placed 60 cm above a table-top. The illuminance at a point on the table-top, directly below the source, is 15 lux. Find the illuminance at a point on the table-top 80 cm away from the first point.


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?


A student is studying a book placed near the edge of a circular table of radius R. A point source of light is suspended directly above the centre of the table. What should be the height of the source above the table so as to produce maximum illuminance at the position of the book?


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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