Tag: physics

Quizzes (598) Questions (13441)

Questions Related to physics

Multiple choice physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

If $v _{g}, v _{x}$, and $v _{m}$ are speeds of gamma rays, $X$ rays, and microwaves respectively in vacuum, then:

  1. $V _{g} < V _{x} < V _{m}$
  2. $V _{g}>V _{x}>V _{m}$
  3. $V _{g} < V _{x}> V _{m}$
  4. $V _{g}=V _{x}=V _{m}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
The gamma rays, $X-$ rays and the microwaves are the Electromagnetic waves and the speed of all the electromagnetic waves remains the same in vacuum irrespective of other parameters. All will travel at the speed of light.

$V _{g}=V _{x}=V _{m}$ 

 The speed of Electromagnetic waves is always the same in vacuum. So, option $(D)$ is correct.

Multiple choice physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

Which of the following electromagnetic waves is used in medicine to destroy cancer cell?

  1. IR- rays

  2. Visible rays

  3. Gamma rays

  4. Ultraviolet rays
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Gamma rays are dominantly used in medicines to destroy the cells that are cancer affected. The gamma rays are chosen such that its energy does not harm the healthy cells.

Therefore, the rays used in medicine to destroy cancer cells are Gamma rays.
Multiple choice physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

A. wavelength of microwave is greater than that of ultraviolet rays.
B. The wave length of infrared rays is lesser than that of ultraviolet rays.
C. wavelength of microwave is lesser than that of ultraviolet rays
D. Gamma rays has shortest wavelength in the electromagnetic spectrum.
Choose the correct option from the given options.

  1. A and B are true

  2. B and C are true

  3. C and D are true

  4. A and D are true
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
The wavelength and the frequency of the Electromagnetic waves are inversely proportional to each other.

$A$. The wavelength of Microwave is greater than UV rays.
The frequency of the microwave is less than that of the Ultraviolet rays, the wavelength of the Microwaves will be longer than the Ultraviolter rays.

$D$. Gamma rays have the shortest wavelength in the EM spectrum.
The frequency of the gamma rays is the highest in the electromagnetic spectrum. So, it will have the shortest wavelength.

The wavelength of the infrared is higher than the Ultraviolet rays and also the wavelength of the microwave is higher than Ultraviolet rays. So, options $B$ and $C$ are not true.
Option $(D)$ is correct.
Multiple choice physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

Which of the following is absorbed by the ozone layer ?

  1. only gamma rays

  2. visible light

  3. radio waves

  4. ultraviolet
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Ozone is a molecule made of three oxygen atom or $O _3$. When ultraviolet light in the range $240nm$ and $320 nm$ strikes an ozone molecule, it absorbs the energy and the $O _3$ changes to $O _2$ and $O$. The $O$ atom soon combines with another $O _2$ molecule to form $O _3$ and is ready to absorb ultra violet light.

Multiple choice physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

What is the type of invisible radiation from space that can be detected from Earth's surface?

  1. Gamma rays

  2. X-rays

  3. Infrared radiation

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

Gamma rays are high-energy electromagnetic radiation from space. While most are absorbed by the atmosphere, they are the standard answer for invisible space radiation detected by specialized instruments.

Multiple choice physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

A potential difference of 0.1kV is applied across an X-ray tube. The ratio of the de-Broglie wave lengths of incident electron, striking the target to the shortest wavelength of X-rays produced nearly (e/m of electron= $1.8\times 10^{11}C/kg$) ?

  1. 1:1

  2. 1:10

  3. 1:100

  4. 1:1000
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The de-Broglie wavelength of an electron is lambda = h / sqrt(2meV). The shortest X-ray wavelength is lambda_min = hc / eV. The ratio lambda / lambda_min = (h / sqrt(2meV)) * (eV / hc) = sqrt(eV / 2mc^2). Plugging in values leads to approximately 1:1000.

Multiple choice physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

Minimum energy that a $\gamma-ray$ must have to give rise to an electron-position pair is

  1. $0.51\ MeV$
  2. $1.02\ MeV$
  3. $2.04\ MeV$
  4. $1.53\ MeV$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Pair production requires a photon with energy at least equal to the total rest mass energy of an electron and a positron. Each has a rest mass energy of approximately 0.51 MeV, so the minimum total energy needed is 2 times 0.51 MeV, which equals 1.02 MeV.

Multiple choice physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

Infrared radiation was discovered in 1860  by

  1. William Wallaston

  2. William Herschel

  3. William Roentgen

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

Herschel was testing filters for the sun so he could observe sun spots. When using a red filter he found there was a lot of heat produced. Herschel discovered infrared radiation in sunlight by passing it through a prism and holding a thermometer just beyond the red end of the visible spectrum.This thermometer was meant to be a control to measure the ambient air temperature in the room. He was shocked when it showed a higher temperature than the visible spectrum. Further experimentation led to Herschel's conclusion that there must be an invisible form of light beyond the visible spectrum.