Dawn of modern Physics

Question 1

Wein’s constant

Answer 1

2.9× 10^ -3 m.K

Question 2

Stefen’s constant

Answer 2

5.67 × 10^-8 W/(m2.T-4)

Question 3

En = nhf

Answer 3

plank’s theory discovered in 1900

Question 4

plank’s constant

Answer 4

6.626 × 10^-34 J.s

This constant is as important as constant c speed of light.

Question 5

Electromagnetic waves were first predicted by?

Answer 5

Maxwell

Question 6

Electromagnetic waves were first produced by?

Answer 6

Hertz

Question 7

Photoelectric effect phenomenon was discovered by?

Experiment for particle nature of light

Answer 7

Hertz

Question 8

Particle nature of light was proposed by?

Answer 8

Max plank

Question 9

Particle nature of light was proven, explained by?

Answer 9

Einstein

Question 10

Plank received nobel prize in ?

Answer 10

1918 for discovery of energy quanta

Question 11

Energy of gamma ray photons?

Answer 11

1 MeV

Question 12

Energy of radiowave photons?

Answer 12

10^-10 eV

Question 13

Relation between radio and gamma photons

Answer 13

10^16 radio photons = 1 gamma photon in energy

Question 14

no of photons from power given?

Answer 14

n = P/E

= P/hf

Question 15

Intensity ? (n

Answer 15

I = P/A 
I= P/ 4 π^2 (surface area)

Question 16

Joule to eV conversion?

eV is the smaller unit

Answer 16

1 eV = 1.6 × 10^-19 J

1 J = 1/ 1.6× 10^-19 eV

Question 17

E (in eV)= 1240 / wavelength (in nm)

Answer 17

E = hc / wavelength

Question 18

stopping potential in photoelectric effect?

Answer 18

reverse (negative) potential at which current becomes zero. (V)

Question 19

Max energy of electrons?

Answer 19

(1/2) mv^2 = V e

Question 20

Threshold frequency and Cutoff wavelength?

Answer 20

Minimum frequency of light for photoelectric effect to occur.
Maximum wavelength of light for photoelectric effect to occur.

Question 21

Work function?

Answer 21

Minimum energy required for electrons to escape the metal surface.

Question 22

E = hf = work function + K.E (max)

Answer 22

hf = hf(threshold) + (1/2) mv^2

Question 23

Explanation of photoelectric effect was given by ? in ?

Answer 23

Albert Einstein in 1905

Question 24

Einstein was awarded nobel prize in?

Answer 24

1921

Question 25

Light used for sodium, potassium, cesium coated silver oxide cathode in photocell?

Answer 25

Na, K = visible light

Cesium coated silver oxide = infrared light

Question 26

Compton effect?

Answer 26

1923 Arthur H Compton.
X-rays bombarded on a Graphite target scattered with larger wavelength.
del lambda called COMPTON SHIFT is difference between their wavelengths.
compton shift = h/mc (1- cos theta)
here m is rest mass of electron.

Question 27

Compton wavelength?

Answer 27

2.43×10^-12 m

Question 28

compton shift at angle 90 degrees and 180 degrees?

Answer 28

compton shift = compton wavelength at 90 degrees

compton shift = 2 compton wavelength at 180 degrees

Question 29

nobel prize for compton on?

Answer 29

1926

Question 30

rest mass of photon?

Answer 30

0

Question 31

mass of photon?

Answer 31

E/c^2 = hf/c^2 = h/c .lambda

Question 32

momentum of photon?

Answer 32

E = pc 
p = E/c 
p = hf/c
p= h/lambda

Question 33

rest mass of electron or positron?

Answer 33

0.51 MeV

Question 34

energy required for pair production?

Answer 34

more than 1.02 MeV

Question 35

no. of photons, mass relation with lambda?

Answer 35

no of photons is directly proportional to lambda

mass inversely proportional to lambda

Question 36

wavelength, frequency, velocity formulas ?

Answer 36

wavelength (nm) = 1240/ V
wavelength (angstrom) = 12400/V
Frequency = 2.4 ×10^14 V
Velocity = 3.5×10^5 (V)^1/2