Unit 5- Radioactivity, Cosmology and Intensity

Question 1

Proton Number

Answer 1

Number of protons in a nucleus

Question 2

Nucleon Number

Answer 2

Number of protons and neutrons in a nucleus

Question 3

Isotopes

Answer 3

Nuclei with the same proton number but different nucleon numbers

Question 4

Activity

Answer 4

Number of decays per unit time

Question 5

Decay Constant

Answer 5

The probability of decay of a nucleus per unit time

Question 6

Half-life

Answer 6

Time for the activity of a sample to halve

Question 7

Binding Energy

Answer 7

Minimum energy to separate all nucleons of a nucleus

Question 8

Binding Energy per nucleon

Answer 8

Minimum energy to separate all nucleons of a nucleus divided by the number of nucleons in the nucleus

Question 9

Hubble’s Law

Answer 9

The speed of recession of a galaxy is proportional to its distance from the observer

Question 10

The Cosmological Principle

Answer 10

On a large scale the universe is uniform (isotropic and homogeneous)

Question 11

Critical Density

Answer 11

The critical density is the density for which the rate of expansion of the Universe tends to zero

Question 12

AU

Answer 12

Mean distance between the Earth and Sun

Question 13

Parsec

Answer 13

Distance from a base length of 1 AU that subtends an angle of 1 arcsecond

Question 14

Doppler Effect

Answer 14

Apparent change in frequency of a wave due to motion of the source or observer

Question 15

Intensity

Answer 15

Power per unit cross-sectional area