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Correct CHOICE is (d) Increases

For explanation I WOULD say: The stopping potential is directly proportional to the frequency of light.

Hence, the stopping potential increases with an INCREASE in the frequency of the INCIDENT light.

Right ANSWER is (c) 5 × 10^14 Hz

The explanation is: Threshold frequency is given as:

v0 = \(\FRAC {W_0}{H}\)

v0 = \(\frac {W_0}{h}\)

v0 = \(\frac {(3.3 \times 10^{-19})}{(6.6 \times 10^{-34})}\)

v0 = 5 × 10^14 Hz.

Right choice is (B) 3 × 10^-19 J

For explanation: GIVEN: λ = 6600 angstrom = 6600 × 10^-10 m.

Energy of a PHOTON = \(\frac {hc}{\lambda }\)

E = \(\frac {(6.6 \TIMES 10^{-34} \times 3 \times 10^8)}{(6600 \times 10^{-10})}\)

E = 3 × 10^-19 J

The CORRECT choice is (c) 4

To explain: There are four types of electron EMISSIONS, namely, thermionic emission, photoelectric emission, SECONDARY emission, and FIELD emission. These are the DIFFERENT methods of producing electron emissions.

Right choice is (c) ELECTRON gun

The explanation is: Davisson – Germer experiment uses an electron gun to produce a fine beam of electrons which can be ACCELERATED to any desired velocity by APPLYING a suitable voltage ACROSS the gun. The others mentioned do not find an APPLICATION here.

The correct choice is (a) True

For explanation: Yes, this is a true statement. In COMPARISON with beta PARTICLE and neutron, the alpha particle has a higher mass, followed by neutron and then beta particle. According to de – Broglie WAVELENGTH EQUATION, the wavelength is inversely proportional to the mass. Hence, the alpha particle has the LOWEST wavelength since it has the highest mass.

The correct choice is (a) Photoelectric effect

Explanation: Photoelectric effect can only be explained based on the particle NATURE of light. This effect is caused DUE to the ejection of ELECTRONS from a metal plate when light FALLS on it. The others do not SHOW the particle nature of light.

The correct option is (a) True

The explanation: Yes, this is a true statement. Solar PANELS work on the basic principle that when light strikes the cathode, it causes the emission of electrons, which in turn will PRODUCE an electric current. Therefore, the PHOTOELECTRIC effect FINDS APPLICATION in solar panels.

The correct answer is (c) Blue LIGHT

For explanation I would SAY: From Einstein’s photoelectric EQUATION, we have

\(\frac {1}{2}\) mv^2 = h(v – v0).

Since the frequency of blue light is greater than that of the red light, blue light EMITS electrons of greater kinetic ENERGY.

The CORRECT answer is (B) CLASSIC wave theory

Explanation: The PRINCIPLE is the classic wave theory. The classic wave theory states that the intensity of LIGHT determines the amplitude of the wave. Therefore, a greater intensity of light will cause the electrons on the metal to oscillate more violently and also to be ejected with greater kinetic energy.

The correct answer is (a) Increases

To explain I WOULD SAY: A photon transfers a part of its energy to the colliding electron, so its energy DECREASES, and consequently wavelength increases. This is because the energy of a photon is inversely PROPORTIONAL to the wavelength of a photon.

Right choice is (B) Violet

Easiest EXPLANATION: According to the equation:

E = \(\frac {hc}{\LAMBDA }\)

Energy is inversely proportional to wavelength. Since a photon in the violet region has the LEAST wavelength, it implies, that photon has the HIGHEST energy.

Correct choice is (a) Electromagnetic theory

The explanation is: According to the electromagnetic theory, the photoelectric effect can be attributed to the TRANSFER of energy from the light to an ELECTRON. From this point of VIEW, an alteration in the intensity of light will induce changes in the kinetic energy of the ELECTRONS emitted from the metal.

The correct choice is (c) 3.770 × 10^21

Best explanation: Given: I = 1500 W/m^2; WAVELENGTH = 5000Å

Required EQUATION ➔ E=hv=\(\frac {hc}{\lambda }\)

Speed of light (c) = 3 × 10^8 m/s

Number of photons/s received = n = \(\frac {IA}{E} = \frac {(1500 \times 1) \times (5000 \times 10^{-10})}{6.63 \times 10^{-34} \times 3 \times 10^8} \)

n = 3.770 × 10^21

Therefore, the number of electrons received per second is 3.770 × 10^21.

Right choice is (C) Violet

To explain: Violet photon has more energy because the energy of a photon is GIVEN as:

E = hv

Since energy is DIRECTLY PROPORTIONAL to wavelength, i.e. vvoilet > vred, the violet photon is more energetic than the red photon.

The correct option is (a) 3.24 × 10^31

To explain I would say: Number of photons EMITTED per SECOND is given as:

N = \( \FRAC {Power}{Energy \, of \, a \, photon} = \frac {P}{HV}\).

N = \( \frac {15 \times 10^3}{6.6 \times 10^{-34} \times 700 \times 10^3}\)

N = 3.24 × 10^31

The correct CHOICE is (b) 0.65 × 10^-10 m

The BEST explanation: Given: charge of PROTON = 1.6 × 10^-19; MASS of proton = 1.6 × 10^-27; V = 2 kV

λ=\(\frac {h}{p} = \frac {h}{\sqrt {2mE}} = \frac {h}{\sqrt {2mqV}}\)

λ=\(\frac {6.6 \times 10^{-34}}{\sqrt {2\times (1.6 \times 10^{-27})\times (1.6 \times 10^{-19}) \times 2000}}\)

λ=0.65 × 10^-12m

Therefore, the wavelength is 0.65 × 10^-12 m.

Correct choice is (a) 1.5 EV

Explanation: Kmax = eV0

Kmax = 1.6 × 10^-19 C × 1.5 V

Kmax = 24 × 10^-19 J

It can also be CONVERTED into units of electron volts that will be:

Kmax = 1.5 eV

Right CHOICE is (d) 8.8 × 10^-35m

Easiest explanation: Given: m = 150 g; v = 50 m/s

The required equation ➔ λ=\(\FRAC {H}{p} = \frac {h}{MV}\)

λ=\(\frac {6.6 \TIMES 10^{-34}}{150 \times 10^{-3} \times 50}\)

λ=8.8 × 10^-35m

The correct CHOICE is (b) λ=\(\frac {h}{p}\)

The explanation is: de – Broglie EQUATION states that matter can act as waves as WELL as particles. So, the de Broglie equation helps us understand the concept of matter having a wavelength. The EXPRESSION forde – Broglie wavelength is given as:

λ=\(\frac {h}{p} = \frac {h}{mv}\)

Where h is the Planck’s constant; p is the momentum; m is the MASS of the particle and v is the velocity of the particle.

The correct option is (a) 0

For EXPLANATION I would SAY: From Einstein’s PHOTOELECTRIC equation, we have

\(\FRAC {1}{2}\) mv^2 = h(v – v0).

When v = v0,

hv0 = hv0 + eV0

Therefore, V0 = 0.

Right choice is (b) \(\FRAC {HC}{\lambda }\)

Explanation: Energy of a photon, E = hv

V = \(\frac {c}{\lambda }\).

THEREFORE, E = \(\frac {hc}{\lambda }\)

Correct option is (b) 0.1 eV

Easy EXPLANATION: Kmax = \(( \FRAC {hc}{\lambda })\) – W0

Kmax = \( [ \frac {(6.6 \TIMES 10^{-34} \times 3 \times 10^8 )}{(6.2 \times 10^{-6} \times 1.6 \times 10^{-19}) }] \) – 0.1.

Kmax = 0.2 – 0.1

Kmax = 0.1 eV

The correct ANSWER is (a) Electron volt

To ELABORATE: One electron volt is the kinetic energy gained by an electron when it is accelerated through a potential difference of 1 volt.

Therefore, 1 eV = 1.602 × 10^-19 J.

Right ANSWER is (a) Metal A

Best explanation: ACCORDING to the equation, W0 = hv0 = \(\frac {hc}{\lambda_0}\), the WORK FUNCTION is inversely proportional to the wavelength.

So metal A with lower work function has a HIGHER threshold wavelength.

The correct answer is (c) ULTRAVIOLET

The best explanation: Ultraviolet rays are most EFFECTIVE for PHOTOELECTRIC emission because they have the HIGHEST frequency when compared to the other electromagnetic waves, and hence the most energetic AMONG all of them.

The CORRECT choice is (B) 2d sin⁡θ=nλ

Explanation: Bragg’s law is a special case of Laue diffraction, it gives the angles for coherent and incoherent scattering from a crystal LATTICE. The expression for Bragg’s law is given as:

2d sin⁡θ=nλ

Right option is (d) DUE to its electromagnetic nature

For explanation: Light TRAVELS as a wave due to its electromagnetic nature. This is further facilitated by Maxwell’s equations which states that changing MAGNETIC fields give rise to ELECTRIC fields and changing electric fields give rise to magnetic fields.

Correct choice is (b) False

To explain I would say: No, this is a false STATEMENT. According to the de – BROGLIE EQUATION, the velocity of the particle and the de – Broglie are inversely proportional to each other. Therefore, when the WAVELENGTH of an electron increases, the velocity of the electron decreases.

Correct answer is (c) \(\frac {1}{\sqrt {5}}\)

To explain: The required equation ➔ λ=\(\frac {H}{mv} = \frac {h}{\sqrt {2mK}} \)

Where h is the Planck’s constant, m is the mass of the electron and K is the KINETIC energy of the electron.

Since the mass of the electron remain unchanged, the wavelength will be inversely proportioned to the kinetic energy, so,

\(\frac {\lambda }{\lambda^{‘}} = \sqrt {\frac {K^{‘}}{K} } = \sqrt { \frac {5K}{K} } \) = √5

Therefore, λ’=\(\frac {\lambda }{\sqrt {5}}\)

HENCE, the wavelength is reduced by a FACTOR of √5.

Correct choice is (c) 1.6 × 10^16 Hz

For explanation I WOULD say: Frequency can be written as, V = \(\frac {E}{h}\)

v = \(\frac {E}{h}\)

v = \(\frac {(66.3 \TIMES 1.6 \times 10^{-19})}{(6.63 \times 10^{-34})} \)

v = 1.6 × 10^16 Hz.

The correct choice is (b) False

Easiest EXPLANATION: No, this is a false statement. The photoelectric EFFECT cannot be explained by wave theory because, in the photoelectric effect, the electron EMISSIONS are immediate without a time delay, WHEREAS in wave theory, the electrons are emitted only after a SMALL instant of time.

Correct ANSWER is (a) True

Best explanation: Yes, this is a true statement. Thermionic emission is the PROCESS of electron emission involving the liberation of electrons from an electrode by virtue of its temperature and this is done by releasing the ENERGY supplied by heat. This happens as the thermal energy given to the CHARGE carrier overcomes the work function of the MATERIAL.

The correct answer is (B) Nickel

To ELABORATE: The CRYSTAL USED in the Davisson – Germer experiment is nickel. A fine beam of electrons is made to fall on the surface of the nickel crystal. As a result, the electrons are scattered in all directions by the atoms of the crystal.

Correct option is (a) Dual NATURE

Explanation: Electromagnetic radiations have a wave nature as well as PROPERTIES ALIKE to those of PARTICLES. Therefore, electromagnetic radiations are emissions with a dual nature, i.e. it has both wave and PARTICLE aspects.

Correct OPTION is (C) No EFFECT

Easiest explanation: No effect. This is because the intensity of radiation incident on a photo-sensitive plate is independent on stopping POTENTIAL. So, the stopping potential remains the same, even if the intensity is DOUBLED.

Correct choice is (a) INCREASING the frequency of the incident beam

Easy explanation: The maximum kinetic energy of the PHOTOELECTRONS can be increased by increasing the frequency of the incident beam and at the same time KEEPING the number of incident photons fixed. Now, this would RESULT in a proportionate increase in energy, and in this way, the maximum kinetic energy can be increased.

Right OPTION is (B) False

Explanation: Kinetic ENERGY = qV.

K = qV

K = e × (1V)

K = 1 eV.

The correct choice is (d) Low work function

The best explanation: Alkali metals have low work functions. Even VISIBLE radiation can EJECT out ELECTRONS from them. So alkali metals are the most suitable photo-sensitive metals.

Right ANSWER is (B) 3 V

For explanation I would say: Stopping potential is given as:

V0 = \(\frac {K_{max}}{E}\)

V0 = \(\frac {3eV}{e}\)

V0 = 3 V

Therefore, the stopping potential is 3 V.

The correct choice is (b) False

To explain: The STOPPING POTENTIAL depends on the FREQUENCY of incident RADIATION. Above the threshold frequency, the stopping potential is directly proportional to the frequency of incident radiation.

The correct answer is (a) Electron emission

Explanation: The process in which an electron escapes from the metal surface is known as electron emission. ELECTRONS are loosely bound to the nucleus, and therefore, a little ENERGY push SETS these electrons flying out of their RESPECTIVE orbits.