The threshold frequency for the ejection of electrons from potassium metal is 5 . 3 × 10 14 s - 1 . Will the photon of a radiation having energy 3 . 3 × 10 - 13 J exhibit the photoelectric effect? h = 6 . 6 × 10 - 34 Js

Threshold frequency is the minimum frequency of incident radiation required to just eject photoelectrons from the surface of the metal. Incident radiation of frequency less than the threshold frequency cannot eject photoelectrons from the metal surface. Energy of incident radiation = 3 . 3 × 10 - 13 J So, hν = 3 . 3 × 10 - 13 ν = 3 . 3 × 10 - 13 6 . 6 × 10 - 34 Hz ν = 5 × 10 20 s - 1 Since, the frequency of incident radiation is more than the threshold frequency, therefore, it will exhibit photoelectric effect.

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Alpha Question Bank for Engineering: Chemistry>Chapter 2 - Structure of Atom>Exercise-4>Q 80

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An electron beam can undergo diffraction by crystals which proves the wave nature of electrons. The potential required for a beam of electrons to be accelerated, so that its wavelength becomes equal to $0.154 nm$ , is:

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Important Questions on Structure of Atom

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Alpha Question Bank for Engineering: Chemistry>Chapter 2 - Structure of Atom>Exercise-4>Q 81

The ratio of the energy of the electron in ground state of hydroqen to the electron in first excited state of

{Be}^{3 +}

is

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Alpha Question Bank for Engineering: Chemistry>Chapter 2 - Structure of Atom>Exercise-4>Q 82

The electrons, identified by quantum numbers $n$ and $l$

$(i) n = 4, l = 1$
$(ii)$ $n = 4, l = 0$

$(iii)$ $n = 3, l = 2$

$(iv)$ $n = 3, l = 1$ can be placed in order of increasing energy, from the lowest to highest, as

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Alpha Question Bank for Engineering: Chemistry>Chapter 2 - Structure of Atom>Exercise-4>Q 83

The energy of an electron in Bohr's orbit of hydrogen atom is

- 13.6 eV

. The total electronic energy of a hypothetical

He

atom is which there are no electron - electron repulsions is:

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Alpha Question Bank for Engineering: Chemistry>Chapter 2 - Structure of Atom>Exercise-4>Q 84

The energy of an electron in the ground state of

H

atom is

- 13.6 eV

. The negative sign indicates that the

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Alpha Question Bank for Engineering: Chemistry>Chapter 2 - Structure of Atom>Exercise-4>Q 85

Why is the cathode ray tube experiment not conducted at atmospheric pressure?

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Alpha Question Bank for Engineering: Chemistry>Chapter 2 - Structure of Atom>Exercise-4>Q 86

The threshold frequency for the ejection of electrons from potassium metal is

5.3 \times 10^{14} s^{- 1}

. Will the photon of a radiation having energy

3.3 \times 10^{- 13} J

exhibit the photoelectric effect?

(h = 6.6 \times 10^{- 34} Js)

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Alpha Question Bank for Engineering: Chemistry>Chapter 2 - Structure of Atom>Exercise-4>Q 87

If the work function

(w)

of an arbitrary metal is

3.1 eV

, find its threshold wavelength and the maximum kinetic energy of the electron emitted when the radiation of

300 nm

strikes the metal surface. (Take

hc = 12400 eV \overset{\circ}{A}

).

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Alpha Question Bank for Engineering: Chemistry>Chapter 2 - Structure of Atom>Exercise-4>Q 88

Calculate the speed of an electron in the ground state of

{He}^{+}

ion. What fraction of speed of light is this value? How long does it take for the electron to complete one revolution around the nucleus. How many times does the electron travel around the nucleus in one second?