Photometry is the measurement of light, defined as electromagnetic radiation that can be detected by the human eye. Photometry is distinct from other measurements of light in the optical field, such as radiometry, which is the science of measuring electromagnetic radiation, including visible light. Photometry is generally based on the eye's photopic response, and thus photometric measurements cannot accurately determine a sources perceived brightness under low-light conditions, when colors are undetectable, like only moonlight or starlight. Photometry is the science and technology of quantifying and measuring light properties related to their perceived brightness to human eyes.
Differential photometry is measuring changes in an object's brightness over time. The measurements are combined in the object's light curve. When measuring an object's brightness across multiple images taken over time, compared stars should be used. When performing photometry, a circle, often called a lens, is placed around each star for which the brightness is to be measured. A general outline of the visual average of human eyesight would be required if any methods were to be developed for measuring or reproducing the colour of the light.
The Photometry short course at NIST covers fundamentals in photometry, radiometry, and colorimetry, and the practical aspects of measuring the light flux, luminous intensity, illuminance, luminosity, color temperature, and chroma of a light source.
Following are some of the multiple choice questions on the Photometry with answers that will help the students in developing their knowledge.
1. In Flame photometry, Flame color’s intensity tells about
2. Which of the following is the advantage of grating monochromators?
3. Which of the following is the advantage of prism monochromators?
4. Laminar flow burner used in Flame photometers is also known as
5. Which of the following is disadvantage of Laminar flow burner used in Flame photometry?
6. In Flame emission photometers, the measurement of _____________ is used for qualitative analysis.
7. Which of the following is the principle of Flame emission photometers?
8. The elements like gold, silver, & inert gases are not analyzed by flame photometry because
9. Flame photometry is mainly used for,
10. In Flame emission photometers, the measurement of _____________ is used for quantitative analysis.
11. Phototubes are more sensitive than photovoltaic cells
12. Which of the following is not an application of Flame emission photometers?
13. At a height of one meter above the centre of a circular table of diameter 4m, a bulb of 100 W hangs. If the intensity at a point on its rim is I0, then what is the intensity at the centre of the table?
14. What is the power of the lamp if its luminous efficiency is 2 lumen/watt and its luminous intensity is 42 candela?
15. Lux is equivalent to which of the following?
16. Which of the following has more luminous efficiency?
17. A lamp hangs at a height of 4 m above a table. The lamp is lowered by 1 m. By how much will the illuminance increase?
18. A point source of 100 candela is held 5 m above a sheet of blotting paper which reflects 75% of the incident light. What is the illuminance of blotting paper?
19. Which of the following sources of light is the inverse square law valid for?
20. Which is application of flame photometry ?
21. Which of the following is not an advantage of Laminar flow burner used in Flame photometry?
22. Which is not application of flame photometry
23. Flame photometry is used for the determination of compositional analysis of_______________?
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