Part 1

Question 1

What does Part 1 of the experiment involve?

Answer 1

Measuring the power of the lamp using thermopile

Question 2

What does the rated output of a light source refer to?

Answer 2

The entire power consumed by it

Question 3

What is luminosity?

Answer 3

Total amount of light emitted by a source

Question 4

What is luminosity proportional to?

Answer 4

The energy consumed

Question 5

What is luminosity dependent on?

Answer 5

Its efficiency

Question 6

Part 1 general method?

Answer 6

1. Turn on lamp and allow to stabilise.
2. Connect thermopile to DMM.
3. Measure voltage vs distance
4. Convert voltage to power using sensitivity
5. Calculate intensity

Question 7

What is the minimum distance between lamp and thermopile? Why?

Answer 7

50cm

As angular aperture of thermopile is only 20 degrees

Question 8

In part 1, how is voltage converted to power?

Answer 8

Using thermopile sensitivity

Question 9

In part 1, how is intensity calculated?

Answer 9

Using power and the effective area of the thermopile

Question 10

How did the measured intensity compare to the power of the lamp?

Answer 10

Large value of luminosity of lamp compared to book value as assumes lamp is a point source, radiating light in all directions

In reality lamp is flat so angle of irritation much smaller giving luminosity in line with stated power