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The MCQs below are drawn from the Physics subject category.
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1261
The wavelength of Lyman series for hydrogen spectrum lies in the
A. ultraviolet region
B. infrared region
C. visible region
D. far-infrared region
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Explanation
The Lyman series involves transitions to the ground state and produces photons in the ultraviolet region.
1262
X-rays and gamma rays of the same energetic beam may be distinguished by
A. their ionising power
B. their velocity
C. their intensity
D. method of production
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Explanation
The essential distinction is their origin: X-rays arise from electronic processes while gamma rays originate from the nucleus.
1263
A crack allows greater amount of X-rays to pass, which appears on photographic film as:
A. Dark Area
B. Red Area
C. Blue Area
D. Bright Area
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Explanation
More X-rays expose the photographic film more, producing a darker region on the developed film.
1264
Whose wavelength is longest in the electromagnetic spectrum?
A. X-rays
B. Infra-red ray
C. Ultraviolet
D. Microwaves
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Explanation
Among the given choices, microwaves have the longest wavelengths (longer than infrared, ultraviolet, and X-rays).
1265
Which of the following is an example of continuous spectra?
A. Blackbody radiation spectrum
B. Molecular spectra
C. Grating spectrum
D. Atomic spectra
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Explanation
A blackbody emits a continuous spectrum over a range of wavelengths rather than discrete lines or bands.
1266
Bremsstrahlung X-rays were fashioned ____ of electrons as they curve around the strong charge of the target nuclei.
A. By the slowing down
B. By moving fast
C. With same speed
D. None of these
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Explanation
Bremsstrahlung X-rays are produced when electrons are decelerated (slowed down) in the Coulomb field of target nuclei.
1267
The process of mixing sound waves with carrier waves is known as
A. demodulation
B. amplification
C. modulation
D. rectification
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Explanation
Mixing the information (sound) signal with a carrier to impose it is called modulation.
1268
X-ray region lies between
A. visible and ultraviolet regions
B. gamma rays and ultraviolet region
C. short radio waves and visible
D. short radio waves and long radio waves
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Explanation
X-rays occupy the region of the electromagnetic spectrum between ultraviolet light and gamma rays.
1269
A radio wave of frequency 840 MHz is sent towards an aeroplane. The frequency of the radio echo is 2.8 kHz more than the original frequency. The velocity of the aeroplane is:
A. 3 km s^-1
B. 4 km s^-1
C. 2 km s^-1
D. 0.5 km s^-1
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Explanation
Radar Doppler shift Δf = 2 v f / c => v = Δf c /(2 f). With Δf=2.8 kHz, f=840 MHz and c≈3×10^8 m/s, v = 500 m/s = 0.5 km s^-1.
1270
Potassium cathode in photocell emit electrons for a light:
A. Infrared
B. X-rays
C. Visible
D. Ultraviolet
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Explanation
The OCR shows a marker next to 'Visible' indicating that the provided material marks visible light as the response for potassium in this context.
