Tag: physics

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Questions Related to physics

Multiple choice physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

The following can be arranged in decreasing order of wave number
A. AM radio
B. TV and FM radio
C. Microwave
D. Short radio wave

  1. A > B > D > C

  2. C > D > B > A

  3. A > B > C > D

  4. D > C > B > A
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Wave number is inversely proportional to wavelength. Decreasing order of wave number means increasing order of wavelength. The order of wavelengths is: Microwave < Short radio wave < TV/FM < AM radio. Therefore, the decreasing order of wave number is C > D > B > A.

Multiple choice physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

A welder wears special glasses to protect his eyes mostly from the harmful effect of 

  1. Very intense visible light

  2. infrared radiation

  3. ultraviolet rays

  4. microwaves.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

During the welding process, the ultra-violet rays are produced which are not visible but have an intense effect on the eyes. Therefore, the welder makes use of the special glass to protect his eyes.

Option (C) is correct.

Multiple choice physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

The wavelengths for the light of red and blue colours are roughly $7.8\times 10^{-7}m$ and $4.8\times 10^{-7}m$ respectively. Which colour has the greater speed in vacuum?

  1. Red

  2. Violet

  3. Yellow

  4. All colors have same speed
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

All electromagnetic waves travels at the same speed in vacuum i.e $3\times10^8$ m/s. Due to the absence of matter, there is no change in speed corresponding to wavelength. There is no absorption and re-emission of light in the absence of matter.

Multiple choice physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

An electromagnetic wave has a frequency of $500MHz$ and a wavelength of $60cm$. Name the medium through which it is traveling.

  1. air

  2. water

  3. salt

  4. cardboard
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The formula for velocity, when given wavelength and the frequency of the wave, is written as: $v=f\lambda $.
In this formula, $f$ represents frequency, $V$ represents the velocity of the wave, and $\lambda $ represents the wavelength of the wave.  
Here, the frequency of the wave is $500 MHz = 500000000 Hz$  and the wavelength is $60 cm = 0.6 m$
Therefore, the velocity of the wave is $3\times { 10 }^{ 8 }m/s$.
This determined velocity is the velocity of the light in air. Hence, the medium through which the wave is travelling is air.

Multiple choice physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

Two waves $A$ and $B$ have wavelength $0.01A^o$ and $9000A^o$ respectively. Compare the speeds of these waves when they travel in vacuum.

  1. $1:9$

  2. $9:1$

  3. $1:1$

  4. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The electromagnetic spectrum consists of the full range of known electromagnetic waves, including gamma rays, X-rays, ultraviolet light, visible light, infrared light, microwaves, and radio waves. All of these are produced by various forms of oscillating charges or currents. Electromagnetic waves are transverse waves which travel at the speed of light and involve oscillating electric and magnetic fields at right angles to each other.
Hence, the speeds of these waves when they travel in vacuum is same as the speed of visible light, that is, $3\times { 10 }^{ 8 }m/s$. Therefore, the ratio of their speeds is $1:1$.

Multiple choice physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

All components of the electromagnetic spectrum in vacuum have the same

  1. energy

  2. velocity

  3. wavelength

  4. frequency
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$Answer:-$ B 

speed of electromagnetic wave in vacuum  is given by:-
c(speed of light)=frequency$\times$ wavelength =$\dfrac{1}{\mu _0 \epsilon _0}$=constant
as we go from gamma rays to radio waves  frequency decreases and wavelength increases thereby maintaining the product constant.

 Energy is given by:- $E=h\nu$ since $\nu$ is different so energy is also different.
Also wavelength and frequency varies.

Multiple choice physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

Earth's atmosphere is transparent for

  1. only the visible light

  2. only the X-rays

  3. only the $\gamma$- rays

  4. visible light and microwaves
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Earth's atmosphere is divided into different layers, out of which the ozone layer absorbs the X-rays and $\gamma$-rays whereas visible light and microwaves are the waves which are not absorbed by any layer of atmosphere.

Multiple choice physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

In an electromagnetic spectrum, if the rays are placed in increasing order with respect to wavelength (i.e., from lower to higher wavelength); The following order is correct

  1. Radiowaves, microwave, infrared rays

  2. Gamma ray, X-ray, ultraviolet ray

  3. Ultraviolet ray, gamma ray, X-ray

  4. Microwave, infrared rays, radiowaves
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The electromagnetic spectrum in increasing order of wavelength is: Gamma rays, X-rays, Ultraviolet, Visible, Infrared, Microwave, Radio waves.