The kinetic energy of the fastest moving photoelectron from a metal of work function 2 . 8 eV is 2 eV . If the frequency of light is doubled, then find the maximum kinetic energy of the photoelectron.

Given, work function ϕ o = 2 . 8 eV , Kinetic energy K E = 2 eV From Einstein photoelectric equation: h ν = ϕ o + K E ⇒ h ν = 2 . 8 + 2 eV = 4 . 8 eV . . . 1 If the incident frequency is doubled 2 ν . Hence, work function remains same ϕ o = 2 . 8 eV , 2 h ν = 2 . 8 eV + K E ⇒ 2 4 . 8 eV = 2 . 8 eV + K E From equation 1 ⇒ K E = 6 . 8 eV .

If applied potential across the X-ray tube is made 2 5 time then minimum wavelength of X-rays is shifted by 1 A o . Find the original values of applied potential and minimum wavelength.

Let the original applied potential and minimum wavelength be V and λ m i n respectively. We know that λ m i n = 12375 V A o . . ( 1 ) Now, when the applied potential is made 2 5 V then, the corresponding wavelength shifts by 1 A o which gives λ m i n + 1 = 12375 2 5 V A o . . ( 2 ) So, from equations 1 and 2 we get; λ m i n λ m i n + 1 = 12375 V 12375 × 5 2 V ⇒ λ m i n λ m i n + 1 = 2 5 ⇒ 5 λ m i n = 2 λ m i n + 2 ⇒ λ m i n = 2 3 = 0 . 66 A o . Also, from equation 1 , we have; 0 . 66 = 12375 V ⇒ V = 12375 0 . 66 = 18750 V = 18 . 75 kV . Hence, the required original wavelength is λ m i n = 0 . 66 A o and appled voltage is V = 18 . 75 kV .

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A metallic surface of the work function $h ν$ is illuminated by a radiation beam of frequency $5 ν$ . The stopping potential observed is $X$ . What will be stopping potential if the surface is illuminated by radiation of $7 ν$ frequency?

Important Questions on Dual Nature of Matter and Radiation

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Beta Question Bank for Medical: Physics>Chapter 32 - Dual Nature of Matter and Radiation>BEGINNER'S BOX - 2>Q 8

The kinetic energy of the fastest moving photoelectron from a metal of work function

2.8 eV

2 eV

. If the frequency of light is doubled, then find the maximum kinetic energy of the photoelectron.

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Beta Question Bank for Medical: Physics>Chapter 32 - Dual Nature of Matter and Radiation>BEGINNER'S BOX - 2>Q 9

A monochromatic light incident on the metal

A

having threshold frequency

ν_{0}

. It emits photoelectrons of maximum kinetic energy

K

. Now the incident frequency is made three times and falls on a metal

B

having threshold frequency

2 ν_{0}

. What will the maximum kinetic energy of photoelectrons be emitted by metal

B

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Beta Question Bank for Medical: Physics>Chapter 32 - Dual Nature of Matter and Radiation>BEGINNER'S BOX - 2>Q 10

If the light of wavelength

4000 \overset{\circ}{A}

falls on a metal that has a stopping potential

1.4 volt

against photoelectric emission, then what is the work function of the metal. [Take

h = 6.6 \times 10^{- 34} J s

and

c = 3 \times 10^{8} m s^{- 1}

]

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Beta Question Bank for Medical: Physics>Chapter 32 - Dual Nature of Matter and Radiation>BEGINNER'S BOX - 2>Q 11

X-rays are produced in a X-ray tube by electrons accelerated through an electric potential difference of 50.0 kV. An electron makes three collisions in the target before coming to rest and loses half of its remaining kinetic energy in each of the first two collisions. Determine the wavelength of the resulting photons. (Neglect the recoil of the heavy target atoms)

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Beta Question Bank for Medical: Physics>Chapter 32 - Dual Nature of Matter and Radiation>BEGINNER'S BOX - 2>Q 12

Voltage applied across the coolidge tube is 25 kV. What is kinetic energy of electron striking at the target and cut-off wavelength of X-ray obtained from the tube ?

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Beta Question Bank for Medical: Physics>Chapter 32 - Dual Nature of Matter and Radiation>BEGINNER'S BOX - 2>Q 13

If applied potential across the X-ray tube is made

\frac{2}{5}

time then minimum wavelength of X-rays is shifted by

\overset{o}{1 A}

. Find the original values of applied potential and minimum wavelength.

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Beta Question Bank for Medical: Physics>Chapter 32 - Dual Nature of Matter and Radiation>BEGINNER'S BOX - 2>Q 14

Find the

(a) maximum frequency, and

(b) minimum wavelength of $X -$ rays produced by $30 kV$ electrons.

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Beta Question Bank for Medical: Physics>Chapter 32 - Dual Nature of Matter and Radiation>BEGINNER'S BOX - 2>Q 15

(a) An X-ray tube produces a continuous spectrum of radiation with its short wavelength end at $0.45 Å$ . What is the maximum energy of a photon in the radiation?

(b) From your answer to (a), guess what order of accelerating voltage (for electrons) is required in such a tube?

A metallic surface of the work function hν is illuminated by a radiation beam of frequency 5ν. The stopping potential observed is X. What will be stopping potential if the surface is illuminated by radiation of 7ν frequency?

Important Questions on Dual Nature of Matter and Radiation

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A metallic surface of the work function $h ν$ is illuminated by a radiation beam of frequency $5 ν$ . The stopping potential observed is $X$ . What will be stopping potential if the surface is illuminated by radiation of $7 ν$ frequency?