Photometry Physics - Photometry

Mark the correct options.

1. Luminous flux and radiant flux have same dimensions.
2. Luminous flux and luminous intensity have same dimensions.
3. Radiant flux and power have same dimensions.
4. Relative luminosity is a dimensionless quantity.

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

1. B > C > A
2. A > C > B
3. B = C > A
4. B = C < A

A light source emits monochromatic light of wavelength 555nm. The source consumes 100W of electric power and emits 35W of radiant flux. Calculate the overall luminous efficiency.

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 (1.0m, 0, 0) in such a way that the normal to the area makes an angle of 37º with the X-axis.

A photographic plate records sufficiently intense lines when it is exposed for 12s to a source of 10W. How long should it be exposed to a 12W source radiating the light of same colour to get equally intense lines?

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

As the wavelength is increased from violet to red, the luminosity:

1. Continuously increases.
2. Continuously decreases.
3. Increases then decreases.
4. Decreases then increases.

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

A source emits light of wavelengths 555nm and 600nm. The radiant flux of the 555nm part is 40W and of the 600nm part is 30W. The relative luminosity at 600nm is 0'6. Find:

1. The total radiant flux.
2. The total luminous flux.
3. The luminous efficiency.

A point source emitting light uniformly in all directions is placed 60cm 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 80cm away from the first point.

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

The illuminance of a small area changes from 900 lumen/m² to 400 lumen/m² when it is shifted along its normal by 10cm. 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.

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?