Wave Motion

31. Which one of the following statements is not correct?

Which one of the following statements is not correct?

Join Our Telegram Channel
The response of the ear to sound of increasing intensity is approximately logarithmic.
The sensitivity of the human ear does not vary with the frequency of sound.
When two or more waves traverse the same medium, the displacement of any element of the medium is the algebraic sum of the displacements due to each wave.
Longitudinal waves can travel in all media—solids, liquids and gases.
This question was previously asked in
UPSC CDS-2 – 2016
Download PDFAttempt Online
The statement that the sensitivity of the human ear does not vary with the frequency of sound is not correct.
– Statement A is correct: The perceived loudness of sound is approximately logarithmic with respect to intensity, which is why the decibel scale (a logarithmic scale) is used.
– Statement B is incorrect: The human ear’s sensitivity is highly dependent on frequency. It is most sensitive to frequencies in the range of 2 kHz to 5 kHz and less sensitive to very low or very high frequencies within the audible range (typically 20 Hz to 20 kHz). This varying sensitivity is represented by equal-loudness contours (Fletcher-Munson curves or ISO 226 curves).
– Statement C is correct: The principle of superposition states that when multiple waves pass through the same medium, the net displacement at any point is the vector sum of the displacements caused by each individual wave. This applies to sound waves.
– Statement D is correct: Longitudinal waves, like sound waves, can travel through solids, liquids, and gases because these media can support compressions and rarefactions. Transverse waves, on the other hand, require a medium that can sustain shear forces, typically solids or the surface of liquids.
The variation in human hearing sensitivity with frequency is important in audio engineering and acoustics. For example, audio equalization is often used to adjust the frequency balance of sound to compensate for the ear’s non-uniform sensitivity.

Subscribe on YouTube

32. Sound and light waves are

Sound and light waves are

Join Our Telegram Channel
respectively longitudinal and transverse in air
respectively transverse and longitudinal in air
both longitudinal in air
both transverse in air
This question was previously asked in
UPSC CDS-1 – 2023
Download PDFAttempt Online
Sound waves are mechanical waves that require a medium (like air, water, or solids) to propagate. In air, sound waves are longitudinal waves, meaning the particles of the medium vibrate back and forth parallel to the direction in which the wave travels, creating regions of compression and rarefaction.
Light waves are electromagnetic waves and do not require a medium to propagate (they can travel through a vacuum). Light waves are transverse waves, meaning the oscillations of the electric and magnetic fields are perpendicular to the direction in which the wave travels.
Therefore, sound waves are longitudinal in air, and light waves are transverse in air (and other media, or vacuum).
– Sound waves are longitudinal in gases and liquids.
– Light waves are always transverse.
While sound waves are longitudinal in air and fluids, they can be both longitudinal and transverse in solids. Other examples of transverse waves include waves on a string and some seismic waves (S-waves). Examples of longitudinal waves include P-waves (a type of seismic wave) and waves in a spring compressed and stretched along its length.

Subscribe on YouTube

33. Which one of the following types of radiation has the shortest

Which one of the following types of radiation has the shortest wavelength?

Join Our Telegram Channel
Radio waves
Visible light
Infrared (IR)
Ultraviolet (UV)
This question was previously asked in
UPSC CDS-1 – 2020
Download PDFAttempt Online
The electromagnetic spectrum consists of various types of radiation ordered by frequency or wavelength. From longest wavelength to shortest wavelength, the order is typically: Radio waves, Microwaves, Infrared (IR), Visible light, Ultraviolet (UV), X-rays, Gamma rays. Comparing the options given: Radio waves have the longest wavelength, followed by Infrared, then Visible light. Ultraviolet (UV) light has a shorter wavelength than visible light. Therefore, among the given options, Ultraviolet (UV) radiation has the shortest wavelength.
– The electromagnetic spectrum is ordered by wavelength and frequency.
– Wavelength and frequency are inversely related ($c = f\lambda$).
– Order of increasing frequency/decreasing wavelength: Radio, Micro, IR, Visible, UV, X-ray, Gamma.
Visible light covers wavelengths from approximately 400 nm (violet) to 700 nm (red). UV wavelengths are shorter than visible light, typically ranging from 10 nm to 400 nm. Infrared wavelengths are longer than visible light, typically from 700 nm to 1 mm. Radio waves have wavelengths ranging from about 1 mm to very long distances.

Subscribe on YouTube

34. If the wavelengths corresponding to ultraviolet, visible and infrared

If the wavelengths corresponding to ultraviolet, visible and infrared radiations are given as λUV, λVIS and λIR respectively, then which one of the following gives the correct relationship among these wavelengths?

Subscribe on YouTube
”λ<sub>UV</sub>
”λ<sub>UV</sub>
”λ<sub>UV</sub>
”λ<sub>UV</sub>
This question was previously asked in
UPSC CDS-1 – 2019
Download PDFAttempt Online
The correct option is D.
The electromagnetic spectrum arranges different types of radiation by wavelength and frequency. Wavelength increases from gamma rays to radio waves. The order of the given radiations by increasing wavelength is: Ultraviolet (UV), Visible, Infrared (IR). Therefore, the correct relationship is λUV < λVIS < λIR.
The approximate wavelength ranges are: UV (10 nm to 400 nm), Visible (400 nm to 700 nm), and IR (700 nm to 1 mm). This confirms the order of wavelengths.

Join Our Telegram Channel
Page 1Page 2Page 3Page 4Page 5