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.

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

1. Moving the source.
2. Rotating the source.
3. Bringing some mirrors in proper positions.
4. Changing the colour of the source.

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.

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:

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.

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?