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Atomic Structure, Multiple Choice Questions

Choose the correct answer.

(i) The e/m ratio of cathode ray is ———- C/kg.

(a) 1.76 &times 1023(b)1.76 &times 1011(c) 1.76 &times 10-31(d) 1.76 &times 107

Correct Option (b)

(ii) ———— determined the charge on an electron.
(a) Millikan (b) J.J Thomson(c) Chadwick(d) Moseley
Correct Option: (a)
(iii) Neutron was discovered by —————-
(a) Chadwick(b)Goldstein(c)J.J Thomson(d)de Broglie
Correct Option: (a)
(iv) The energy associated with quantum of radiation is —————–
(a)hν(b) nh/2π(c) 2hν(d) 1/2 × hν
Correct Option: (a)
Note: ν is the frequency of radiation.

(v) What will be the wave number of a radiation with λ = 2 × 108 nm?

(a) 0.5 × 10-8 nm(b) 10 nm(c) 5 nm(d) 100 nm

Correct Option: (a)
Solution: Wave number = 1/λ = 1/(2×108 nm) = 1/2 × 10-8 nm = 0.5 × 10-8 nm

(vi) Which of the following is not electromagnetic in nature?

(a) IR rays(b) X-rays(c) γ rays(d) cathode rays

Correct Option: (d)

Explanation: All electromagnetic radiations are in the range of frequencies of about 3 × 1026 Hz to 3 × 103 Hz. They are further divided into 7 regions containing γ-rays, X-rays, ul (ultra violet) rays, visible light, IR (infra-red), microwaves and radio waves. Cathode rays does not include them.

(vii) Frequency of a green light is 6 × 1014 Hz. Its wave length is ———

a)      500 nm

b)      5 nm

c)       5000 nm

d)      100 nm

Solution

c=fλ ⇒ λ = c/f ⇒ λ = (3×108)/(6×1014) ⇒ λ = 0.5×10-6 ⇒ λ = 500 × 10-9 m = 500 nm

(viii) If the mass of electron is reduced to half, the Rydberg’s constant …..

(a) becomes half(b) becomes double(c) remains unchanged(d) becomes one fourth

Correct Option: (a)

(ix) Which of the following is the mathematical form of Moseley’s law:

(a) √ν = b(z – a)(b) √ν = a(z – b)(c) √ν = a/b √z(d) √ν = b/z.z

Correct Option: (b)

(x) For which of the following species, Bohr’s theory does not apply?

(a) H(b) H+(c) He+(d) Li++

Correct Option: (b)

(xi) Which of the following set of four quantum numbers is correct for an electron in K-shell?

(a) n =1, ℓ = 0, m =0, s = +1/2(b) n = 2, ℓ = 1, m = 0, s = +1/2(c) n = 1, ℓ = 1, m = 0, s = -1/2(d) n = 2, ℓ = 2, m = +2, s = +1/2

Correct Option: (a)

(xii) The splitting of spectral line in the presence of magnetic field is called …..

(a) Stark effect(b) Zeeman effect(c) Uncertainty Principle(d) Hund’s rule

Correct Option; (b)

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