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1211
The product of Am and T is called:
A. Pringshein's constant
B. Planck's constant
C. Lummer's constant
D. Wien's constant
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Correct Option
Explanation
Wien's displacement law states that the product of the wavelength of maximum emission (λm) and temperature (T) is a constant called Wien's constant.
1212
In Q.32, if V_s is the stopping potential in the first case, then the stopping potential in the second case will be:
A. 12 V_s
B. V_s
C. 9 V_s
D. 3 V_s
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Correct Option
Explanation
The OCR answer key for this question indicates option B (3 V_s) as the stopping potential in the second case.
1213
The energy of an X-ray photon of wavelength 1.65 Å is
A. 5.5 keV
B. 7.5 keV
C. 3.5 keV
D. 9.5 keV
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Explanation
E (keV) ≈ 12.4 / λ(nm); with λ = 1.65 Å = 0.165 nm, E ≈ 7.5 keV.
1214
Which one of the following could be the frequency of ultraviolet radiation?
A. 1.0 × 10^18 Hz
B. 1.0 × 10^12 Hz
C. 1.0 × 10^15 Hz
D. 1.0 × 10^21 Hz
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Explanation
Ultraviolet radiation has frequencies around 10^15 Hz, so 1.0 × 10^15 Hz is the plausible UV frequency.
1215
The velocity of light in air is 3 × 10^10 cm s⁻¹. What is the frequency and the wavelength of a beam of light in a diamond of refractive index μ = 2.4, if wavelength of light in air is 4800 Å?
A. 6.25 × 10^14 Hz, 2000 Å
B. 6.25 × 10^13 Hz, 200 Å
C. 6.25 × 10^15 Hz, 200 Å
D. 6.25 × 10^15 Hz, 2000 Å
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Correct Option
Explanation
Frequency = v/λ = 3×10^10 cm/s ÷ 4.8×10^-5 cm = 6.25×10^14 Hz; wavelength in diamond = 4800 Å / 2.4 = 2000 Å, so option A.
1216
Band spectrum is produced by
A. H
B. He
C. Na
D. H2
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Explanation
Band spectra arise from molecular electronic transitions; diatomic molecules like H2 produce band structures.
1217
Consider electrons and protons accelerated in a vacuum tube across the same potential difference. Which of the following is true ?
A. protons have larger kinetic energy
B. protons have smaller momentum
C. electrons have smaller velocity
D. protons and electrons have same kinetic energy
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Explanation
Both acquire the same kinetic energy equal to the charge times the potential difference (eV), regardless of mass.
1218
The wavelength of Paschen series lies in the
A. ultraviolet region
B. visible region
C. infrared region
D. invisible region
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Explanation
The Paschen series involves transitions to the n=3 level and emits photons in the infrared region.
1219
The X-ray beam coming from an X-ray tube will be
A. monochromatic
B. having all wavelengths between a minimum and a maximum
C. having all wavelengths smaller than a certain maximum wavelength
D. having all wavelengths larger than a certain minimum wavelength
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Explanation
A typical X-ray tube emits a continuous spectrum containing all wavelengths larger than the short-wavelength cutoff (the minimum wavelength).
1220
Which of the following forms of electromagnetic energy has the longest wavelength?
A. Infrared waves
B. Visible light
C. Radiowaves
D. Microwaves
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Explanation
Radiowaves occupy the longest-wavelength portion of the electromagnetic spectrum.
