Ch. 4: Photometry

Question 1

what does the photopic luminosity curve explain?

Answer 1

shows that certain wavelengths are more efficient at stimulating the visual system than others

Question 2

what is concerned with the power produced by a source of electromagnetic radiation, irrespective of its effect on vision?

Answer 2

radiometry

Question 3

what deals with the effect that this radiation has on the visual system?

Answer 3

photometry

Question 4

is it possible that both a 400 nm and 600 nm patch of ligth emit the same radiant power? how about luminous power?

Answer 4

yes both can emit 10 W (radiant power)

but 600 nm emits more lumens than a 400 nm power.

Question 5

what does Abney’s Law of Additivity describe?

Answer 5

luminous power for such a stimulus is determined by calculating the number of lumens produced by each wavelength and then adding these values together.

Question 6

what is luminous intensity?

Answer 6

refers to the number of lumens produced in a given direction by a point light source

Question 7

what is luminance?

Answer 7

the amount of light coming off a surface such as a piece of paper, in a specified direction.

Question 8

what is illuminance?

Answer 8

refers to the luminous power that falls on a surface (illuminance is not affected by the surface on which the light falls).

Question 9

is it true that luminance refers to the light coming off the surface and illuminance refers to the amount of light falling on a surface?

Answer 9

yes

Question 10

what 2 test follow Abney’s law of additivity?

Answer 10

HFP and MDB

Question 11

does incandescent source produce light through the excitation of individual atoms?

Answer 11

no. a luminescent source does

Question 12

what is the task in HFP?

Answer 12

to adjust the radiance of the sample stimulus such that the flicker is minimized (once completed the standard and sample wavelengths are at equal luminance)

Question 13

what is the task in MDB (minimally distinct border)?

Answer 13

to adjust the radiance of the sample so that the visibility of the border is minimized. end point is when border exists only due to chromatic contrast (luminance contrast has been eliminated)

Question 14

what is a blackbody radiator?

Answer 14

a theoretical construct that has proven convenient for describing sources of electromagnetic radiation, including light sources

Question 15

what is the term used to describe incandescent light sources?

Answer 15

color temperature (CT)

Question 16

is it true that the correlated color temperature of a fluorescent light tube depends on the nature of the phosphor that coats the bulb?

Answer 16

yes

Question 17

what is unique about long-pass filters?

Answer 17

they only transmit long wavelengths of light

Question 18

T/F? in narrowband filters is it true that the smaller the half-height bandwidth the more selective the filter?

Answer 18

true

Question 19

What is the unit for luminous energy?

Answer 19

lumen second (lm x s)

Question 20

What is the unit for luminous flux?

Answer 20

lumen (cd x sr) = lm

Question 21

What is the unit for luminous intensity?

Answer 21

candela (lm/sr) = cd

Question 22

What is the unit for luminance?

Answer 22

candela per square metre = cd/m^2

Question 23

What is the unit for illuminance?

Answer 23

lux (lm/m^2) = lx

Question 24

What is the unit for luminous emittance?

Answer 24

lux (lm/m^2) = lx

Question 25

What is the unit for luminance efficacy?

Answer 25

lumens per watt