The wavenumber of a photon in the Brackett series of a hydrogen atom is \(\frac{9}{400}R.\) What is the quantum number of the electron that has transited from the orbit?
1. \(5\)
2. \(6\)
3. \(4\)
4. \(7\)

Subtopic:  Spectral Series |
 63%
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In an experiment to determine the e/m value for an electron using Thomson's method the electrostatic deflection plates were 0.01 m apart and had a potential difference of 200 volts applied. Then the electric field strength between the plates is 

1. 1×104 V/m 

2. 2×104 V/m

3. 4×104 V/m 

4. 5×105 V/m

Subtopic:  Various Atomic Models |
 87%
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Hydrogen \({}_{1}\mathrm{H}^{1}\), Deuterium \({}_{1}\mathrm{H}^{2}\), singly ionised helium \(\left({}_{2}\mathrm{He}^{4}\right)^+\), and doubly ionised lithium\(\left({}_{3}\mathrm{Li}^{6}\right)^{+++}\) all have one electron around the nucleus. Consider an electron transition from \(n=2\) to \(n=1\). If the wavelengths of emitted radiations are \(\lambda_1, \lambda_2, \lambda_3~\text{and}~\lambda_4\) respectively, then approximately which one of the following is correct?
1. \(4 \lambda_1=2 \lambda_2=2 \lambda_3=\lambda_4\)
2. \( \lambda_1=2 \lambda_2=2 \lambda_3=\lambda_4\)
3. \( \lambda_1=\lambda_2=4 \lambda_3=9\lambda_4\)
4. \( \lambda_1=2\lambda_2=3 \lambda_3=\lambda_4\)

Subtopic:  Bohr's Model of Atom |
 78%
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To explain his theory, Bohr used

1. conservation of linear momentum

2. conservation of angular momentum

3. conservation of quantum  frequency

4. conservation of energy

Subtopic:  Bohr's Model of Atom |
 86%
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Bragg's law for X-rays is:

1. dsinθ = 2nλ 

2. 2dsinθ = nλ

3. nsinθ = 2λd

4. None of these

Subtopic:  X-Ray (OLD NCERT) |
 85%
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The minimum wavelength of X-rays produced by electrons accelerated by a potential difference of V volt is equal to 

1. eVhc 

2. ehcV 

3. hceV 

4. cVeh

Subtopic:  X-Ray (OLD NCERT) |
 83%
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The graph between the square root of the frequency of a specific line of the characteristic spectrum of X-rays and the atomic number of the target will be:

1.

2. 

3. 

4. 

Subtopic:  X-Ray (OLD NCERT) |
 54%
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The wavelength of Kα X-rays for lead isotopes Pb208, Pb206, Pb204 are λ1, λ2 and λ3 respectively. Then

1. λ1=λ2>λ3   

2. λ1>λ2>λ3

3. λ1<λ2<λ3 

4. λ2=λ1=λ3

Subtopic:  X-Ray (OLD NCERT) |
 57%
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which of the following is positively charged?

1.  α-particles  

2.  β-particles  

3.  γ-rays  

4.  X-rays

Subtopic:  X-Ray (OLD NCERT) |
 85%
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A X-ray tube operates at an accelerating potential of 20 kV. Which of the following wavelength will be absent in the continuous spectrum of X-rays?

1.  12 pm

2.  75 pm

3.  65 pm

4.  95 pm

Subtopic:  X-Ray (OLD NCERT) |
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