Exam IV Vocabulary

Question 1

critical angle

Answer 1

the minimum angle of incidence inside a medium at which a light ray is totally reflected

Question 2

refraction

Answer 2

the bending of an oblique ray of light when it passes from one transparent medium to another

Question 3

diffraction

Answer 3

the bending of light that passes near the edge of an object or through a narrow slit, causing the light to spread

Question 4

total internal reflection

Answer 4

the total reflection of light traveling within a denser medium when it strikes the boundary with a less dense medium at an angle larger than the critical angle

Question 5

convex lense

converging

Answer 5

a lens that is thicker in the middle than at the edges and that refracts parallel rays to & fo

Question 6

concave lense

diverging

Answer 6

a lens that is thinner in the middle than at the edges, causing parallel rays to diverge as if from a point

Question 7

virtual image

Answer 7

an image formed by light rays that do not converge at the location of the image

Question 8

real image

Answer 8

an image formed by light rays that converge at the location of the image. a real image, unlike a virtual image, can be displayed on a screen

Question 9

huygen’s principle

Answer 9

every point on a wavefront may be considered the source of secondary wavelets that spread out in all directions with a speed equal to the speed of propagation of the wave

Question 10

superposition

Answer 10

the overlapping and combining of waves

Question 11

radioactivity

Answer 11

the sponatneous emission of energetic particles by an atomic nucleus

Question 12

alpha ray

α-ray

Answer 12

a stream of alpha particles (helium nuclei) ejected by certain radioactive elements

Question 13

beta ray

β-ray

Answer 13

a stream of electrons emitted during the radioactive decay of certain nuclei

Question 14

gamma ray

γ-ray

Answer 14

high frequency electromagnetic radiation emitted by the nuclei of radioactive atoms

Question 15

half-life

Answer 15

the time required for half the atoms in a sample of radioactive isotope to decay

Question 16

electron

Answer 16

the negative particle in the outer part of the atom

Question 17

rad

Answer 17

The acronym (radiation absorbed dose) for a unit of absorbed energy

Question 18

rem

Answer 18

The acronym (roentgen equivalent man) for a unit used to measure the effect of ionizing radiation on humans

Question 19

nuclear fission

Answer 19

the splitting of the nucleus of a heavy atom, such as uranium-235, into two smaller nuclei, accompanied by the release of much energy

Question 20

nuclear fusion

Answer 20

the combination of light atomic nuclei to form heavier nuclei often with release of much energy

Question 21

strong nuclear force

Answer 21

the force that attracts nucleons to each other within the atomic nucleus; a force that is very strong at close distances and greatly weakens as distance increases

Question 22

radiation detectors

geiger + scintillation counters & cloud + bubble chambers

Answer 22

1. geiger counter detects incoming radiation by a short pulse of current triggered when radiation ionizes a gas in the tube.
2. scintillation counter indicates incoming radiation by flashes of light produced when charged particles or gamma rays pass through the counter.
3. cloud chamber: charged particles moving through supersaturated vapor leaves trails
4. bubble chamber: liquid hydrogen is heated under pressure in a glass and stainless steel chamber to a point just short of boiling.