physics MCQs - 12th class Chapter 09 Mcqs

1

The branch of physics that deals with the investigation of wavelengths and intensities of electromagnetic radiation emitted or absorbed by atoms is called?

A

Optics

B

Spectroscopy

C

Quantum Physics

D

Relativity

2

Which of the following is an example of a continuous spectrum?

A

Atomic spectrum

B

Molecular spectrum

C

Black body radiation spectrum

D

Line spectrum

3

The first spectral series of hydrogen identified, which lies in the visible region, is the?

A

Lyman series

B

Paschen series

C

Brackett series

D

Balmer series

4

What is the value of the Rydberg's constant, R_H?

A

1.0974 x 10^7 m⁻¹

B

6.63 x 10⁻³⁴ Js

C

9.1 x 10⁻³¹ kg

D

3 x 10⁸ m/s

5

The Lyman series of the hydrogen spectrum lies in which region?

A

Visible

B

Infrared

C

Ultraviolet

D

Microwave

6

The Paschen, Brackett, and Pfund series of hydrogen are found in which region?

A

Infrared

B

Visible

C

Ultraviolet

D

X-ray

7

According to Bohr's first postulate, an electron moving in a discrete stationary state does what?

A

Emits radiation continuously

B

Absorbs radiation continuously

C

Does not radiate energy

D

Jumps to a higher orbit

8

Bohr's second postulate states that the orbital angular momentum of an electron is an integral multiple of?

A

h

B

h/π

C

h/2π

D

2π/h

9

According to Bohr's third postulate, when an electron jumps from a high energy state E_n to a lower energy state E_p, it emits a photon of energy?

A

E_n + E_p

B

E_n / E_p

C

E_p - E_n

D

E_n - E_p

10

Who gave the interpretation of Bohr's orbits in terms of standing de Broglie waves?

A

Planck

B

Rydberg

C

Heisenberg

D

de Broglie

11

For a standing wave to exist in a circular orbit of radius r, the circumference 2πr must be equal to?

A

nλ/2

B

nλ

C

(n+1/2)λ

D

λ/n

12

The radius of the first Bohr orbit in a hydrogen atom is approximately?

A

0.053 nm

B

0.53 nm

C

5.3 nm

D

0.0053 nm

13

The radius of the nth stationary orbit in a hydrogen atom is proportional to?

A

n

B

1/n

C

n²

D

1/n²

14

The energy of an electron in the ground state (n=1) of a hydrogen atom is?

A

-3.4 eV

B

-1.51 eV

C

-13.6 eV

D

13.6 eV

15

The energy required to completely remove an electron from an atom is called?

A

Excitation potential

B

Excitation energy

C

Binding energy

D

Ionization energy

16

An atom is in an excited state when its electron is in?

A

The ground state

B

A higher orbit than the ground state

C

The nucleus

D

A free state

17

The formula 1/λ = R_H (1/p² - 1/n²) describes?

A

The radii of Bohr orbits

B

The energy of Bohr orbits

C

The wavelength of the hydrogen spectrum

D

The speed of an electron

18

Inner shell transitions in heavy atoms give rise to the emission of?

A

Visible light

B

Infrared radiation

C

Ultraviolet radiation

D

X-rays

19

In an X-ray tube, electrons are emitted from the?

A

Anode

B

Filament (Cathode)

C

Tungsten target

D

Cooling oil

20

The continuous X-ray spectrum is produced by an effect known as?

A

Photoelectric effect

B

Compton effect

C

Bremsstrahlung

D

Pair production

21

Bremsstrahlung is also known as?

A

Characteristic radiation

B

Braking radiation

C

Induced radiation

D

Spontaneous radiation

22

In a CAT-Scanner, the 'C' and 'A' stand for?

A

Computerized Axial

B

Calculated Atomic

C

Carbon-Argon

D

Cathode-Anode

23

Which of the following can be detected with a CAT-Scan?

A

Density differences of about 1%

B

Only fractured bones

C

Only large tumors

D

Electrical activity of the brain

24

Excessive exposure to X-rays can cause?

A

Stronger bones

B

Improved vision

C

Cancer

D

No harm

25

Heisenberg's Uncertainty Principle gives a fundamental limitation on the simultaneous measurement of?

A

Energy and time

B

Mass and velocity

C

Position and momentum

D

Charge and mass

26

Based on the uncertainty principle, an electron cannot be confined within?

A

An atom

B

An orbit

C

A shell

D

A nucleus

27

What does the acronym LASER stand for?

A

Light Amplification by Spontaneous Emission of Radiation

B

Light Absorption by Stimulated Emission of Radiation

C

Light Amplification by Stimulated Emission of Radiation

D

Light Amplification by Stimulated Ejection of Radiation

28

The process where a photon is absorbed by an atom, causing it to move to an excited state, is called?

A

Spontaneous emission

B

Stimulated emission

C

Induced absorption

D

Population inversion

29

An excited state with a relatively long lifetime (e.g., 10⁻³ s) is called a?

A

Ground state

B

Normal excited state

C

Metastable state

D

Ionized state

30

The condition where more atoms are in a higher energy state than in a lower energy state is called?

A

Thermal equilibrium

B

Population inversion

C

Stimulated absorption

D

Spontaneous decay

31

In a laser, what is used to confine photons and stimulate further emission?

A

Lenses

B

Slits

C

Mirrors

D

A magnetic field

32

In a Helium-Neon laser, which element is the lasing or active medium?

A

Helium

B

Neon

C

Argon

D

A mixture of both

33

The metastable state in Helium is at 20.61 eV, and in Neon it is at?

A

18.70 eV

B

20.61 eV

C

20.66 eV

D

1.96 eV

34

The red laser light from a He-Ne laser has a wavelength of approximately?

A

532.8 nm

B

632.8 nm

C

732.8 nm

D

432.8 nm

35

Population inversion in a He-Ne laser is achieved through?

A

Optical pumping

B

Direct electrical excitation of Neon

C

Collisions with excited Helium atoms

D

Chemical reaction

36

Which of the following is a use of lasers in medicine?

A

Measuring blood pressure

B

Welding detached retinas

C

Analyzing blood type

D

Standard vaccinations

37

The process of generating three-dimensional images of objects using a laser beam is called?

A

Tomography

B

X-ray imaging

C

Spectroscopy

D

Holography

38

The energy of the photon emitted by a He-Ne laser is approximately?

A

20.66 eV

B

18.70 eV

C

1.96 eV

D

0.05 eV

39

Shadow of bones on an X-ray film appears lighter than the surrounding flesh because bones?

A

Absorb fewer X-rays

B

Absorb more X-rays

C

Reflect X-rays

D

Are transparent to X-rays

40

The photons emitted in inner shell transitions are called characteristic X-rays because their energies depend on the?

A

Applied voltage

B

Filament temperature

C

Type of target material

D

Size of the vacuum tube

41

A K_α X-ray is produced when an electron jumps from the?

A

M shell to K shell

B

L shell to K shell

C

L shell to M shell

D

M shell to L shell

42

The minimum wavelength in a continuous X-ray spectrum depends on the?

A

Target material

B

Kinetic energy of impacting electrons

C

Filament current

D

Angle of emission

43

A state corresponding to n=1 in a hydrogen atom is called the?

A

Excited state

B

Metastable state

C

Ionized state

D

Ground state

44

For the Balmer series, the electron transitions end at the principal quantum number?

A

p = 1

B

p = 2

C

p = 3

D

p = 4

45

For the Lyman series, the electron transitions end at the principal quantum number?

A

p = 1

B

p = 2

C

p = 3

D

p = 4

46

The fact that atomic spectra consist of discrete lines was used in the 19th century for?

A

Generating electricity

B

Identifying different elements

C

Measuring the speed of light

D

Understanding gravity

47

In stimulated emission, the emitted photon travels in what direction relative to the incident photon?

A

Opposite direction

B

Perpendicular direction

C

The same direction

D

A random direction

48

In a He-Ne laser, population inversion in neon is sustained relative to which energy level?

A

20.66 eV

B

20.61 eV

C

18.70 eV

D

Ground state

49

The discrete, stationary orbits in Bohr's model are those where electrons can move without?

A

Gaining speed

B

Losing speed

C

Radiating energy

D

Changing direction