Which of the following is a source of ultraviolet light?

Question

1. electric bulb
2. red hot iron ball
3. carbon arc lamp
4. sodium vapour lam

Answer 1

3 is correct

1 gives visible light
2 gives red light
4 gives yellow light

Answer 2

3

Answer 3

All of the sources produce some UV. The electric bulb and the iron ball behave as thermal sources with a continuous spectrum described by the Planck law for black body radiation. As the temperature increases, the intensity of radiation increases as T^4 (Stefan-Boltzmann Law) and the wavelength of maximum emission shifts to shorter wavelengths. The carbon arc lamp and the sodium vapour lamp both produce discrete atomic emission line spectra and UV transitions are present in both. The relative intensities of the lines will depend upon the populations in the various quantum states. There will be more UV transitions at higher temperatures.

The amount of UV observed depends to a great extent upon the material used to contain the lamp. Most lamps are made with glass designed to absorb UV. This eliminates the electric bulb and the sodium vapour lamp. The iron ball is a weak source of UV because the temperature is relatively low. Most carbon arc lamps (fluorescent bulbs) have glass designed to absorb UV (and re-emit at longer wavelengths-fluorescence), but there are some lamps specifically designed to transmit UV. These are black light bulbs approx. 370 nm and germicidal bulbs approx. 255 nm. Generally, a bulb with a quartz shell will transmit in the UV region.

Answer 4

the answer is 3

Answer 5

red hot iron ball