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.

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

1. Energy of light entering the eye per second.
2. Wavelength of the light.
3. Total radiant flux entering the eye.
4. Total luminous flux entering the eye.

Figure shows a small diffused plane source S placed over a horizontal table-top at a distance of 2.4m with its plane parallel to the table-top. The illuminance at the point A directly below the source is 25 lux. Find the illuminance at a point B of the table at a distance of 1.8m from A.
 

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

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.

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?

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.

A bulb is hanging over a table. At which portion of the table is the illuminance maximum? If a plane mirror is placed above the bulb facing the table, will the illuminance on the table increase?

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.

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.

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.

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

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?