#### 12th Standard Physics Dual Nature of Radiation and Matter English Medium Free Online Test One Mark questions 2020 - 2021

12th Standard

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Physics

Time : 00:20:00 Hrs
Total Marks : 20

20 x 1 = 20
1. The wavelength λe of an electron and λp of a photon of same energy E are related by

(a)

λp $\alpha$ λe

(b)

${ \lambda }_{ p }\alpha \sqrt { { \lambda }_{ e } }$

(c)

${ \lambda }_{ p }\alpha \frac { 1 }{ \sqrt { { \lambda }_{ e } } }$

(d)

${ \lambda }_{ p }\alpha { \lambda }_{ e }^{ 2 }$

2. A light source of wavelength 520 nm emits 1.04 × 1015 photons per second while the second source of 460 nm produces 1.38 × 1015 photons per second. Then the ratio of power of second source to that of first source is

(a)

1.00

(b)

1.02

(c)

1.5

(d)

0.98

3. Photons of wavelength λ are incident on a metal. The most energetic electrons ejected from the metal are bent into a circular arc of radius R by a perpendicular magnetic field having magnitude B. The work function of the metal is

(a)

$\frac { hc }{ \lambda } -{ m }_{ e }+\frac { e^{ 2 }{ B }^{ 2 }{ R }^{ 2 } }{ { 2m }_{ e } }$

(b)

$\frac { hc }{ \lambda } +{ 2m }_{ e }{ \left[ \frac { eBR }{ { 2m }_{ e } } \right] }^{ 2 }$

(c)

$\\ \frac { hc }{ \lambda } -{ m }_{ e }{ c }^{ 2 }-\frac { e^{ 2 }{ B }^{ 2 }{ R }^{ 2 } }{ { 2m }_{ e } }$

(d)

$\frac { hc }{ \lambda } -{ 2m }_{ e }{ \left[ \frac { eBR }{ { 2m }_{ e } } \right] }^{ 2 }$

4. Emission of electrons by the absorption of heat energy is called_______emission.

(a)

photoelectric

(b)

field

(c)

thermionic

(d)

secondary

5. P and E denote the linear momentum and energy of a photon. If the wavelength is decreased

(a)

Both P and E increase

(b)

P increases and E decreases

(c)

P decreases and E increases

(d)

both P & E decrease

6. ______ is the basis for the electron microscope.

(a)

Matter waves

(b)

Integral wavelength

(c)

Circular orbits

(d)

Electron mass

7. The third electromagnet put in the path of an electron beam in an electron microscope is called _________

(a)

projector magnetic lens

(b)

accelerator

(c)

velocity selector

(d)

oscilloscope

8. Newtonian mechanics regarded that space existed _________

(a)

with reference to objects

(b)

as a variable

(c)

without any reference to objects

(d)

as only vacuum

9. Fixed frames of reference are used in _____

(a)

general theory of relativity

(b)

classical mechanics

(c)

statistical mechanics

(d)

special theory of relativity

10. The number of reference frames in our universe is _______

(a)

3

(b)

2

(c)

zero

(d)

infinite

11. Lorentz-Pitzgerald contraction occurs in _______ direction of motion.

(a)

the same

(b)

a perpendicular

(c)

random

(d)

no

12. The change in kinetic energy of the particle is proportional to ________

(a)

change in its mass

(b)

its mass

(c)

its velocity

(d)

its velocity change

13. Nuclear fission and fusion processes are examples of _______

(a)

Newton's laws

(b)

mass-energy equivalence

(c)

gravitational laws

(d)

Maxwell's laws

14. Wavelength of X-rays is ______ the wavelength of visible light

(a)

smaller than

(b)

greater than

(c)

negligible when compared to

(d)

equal to

15. Find the kinetic energy if hv = 2.1 eV and work function is given as 5 x 10-19J

(a)

0.288 eV

(b)

0.288 J

(c)

1.025 eV

(d)

5 eV

16. If the potential difference is increased by 9 times, the de-Broglie wavelength becomes ________ times the original.

(a)

$\frac{1}{3}$

(b)

3

(c)

9

(d)

$\frac{1}{9}$

17. The length of a moving scale is 6 m, whose velocity is 2 x 107 m/s. Find its rest length.

(a)

7.6 m

(b)

15 m

(c)

3 m

(d)

6.013 m

18. The number of de Brogle waves of an electron in the nth orbit of an atom is

(a)

n

(b)

n-1

(c)

n+1

(d)

2n

19. The length of the rod placed inside a rocket is measured as 1 m by an observer inside the rocket which is at rest. When the rocket moves with a speed of 36 x 106 km/hr the length of the rod as measured by the same observer is

(a)

0.997 m

(b)

1.003 m

(c)

1 m

(d)

1.006 m

20. The number of waves in a distance l is equal to:

(a)

frequency

(b)

3 x 108

(c)

wave number

(d)

1