Tag: physics

Questions Related to physics

Identify which of the following wave has the longest frequency?

physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

  1. Red light

  2. Blue light

  3. Gamma rays

  4. X rays

  5. Radio waves

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Correct Option: C
Explanation:

If we observe the electromagnetic spectrum , we see that gamma rays has the highest frequency.

PAR range of wavelength is 

physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

  1. $400-700 nm$

  2. $400-800 nm$

  3. $450-950 nm$

  4. $500-600 nm$

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Correct Option: A
Explanation:

Photosynthetically Active Radiation $(PAR)$ Is the amount of light available for photosynthesis, which is light in the $400$ to $700$ nanometer wavelength range. PAR changes seasonally and varies depending on the latitude and time of day.

Electromagnetic waves that include light belong to

physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

  1. light spectrum.

  2. electronic spectrum.

  3. electromagnet group.

  4. electromagnetic spectrum.

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Correct Option: D
Explanation:

Electromagnetic waves do not include light belong to electromagnetic spectrum.

The the basic source of electromagnetic waves is an accelerated charge. This produces the changing electric and magnetic field which constitutes electromagnetic wave. An electromagnetic wave may have its wavelength varying from zero to infinity. The classification of electromagnetic waves according to frequency or wavelength is called the electromagnetic spectrum.

In electromagnetic spectrum, the frequencies of $\gamma$-rays and ultraviolet rays are denoted by $n _1, n _2$ and $n _3$ respectively then.

physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

  1. $n _1 > n _2 > n _3$

  2. $n _1 < n _2 < n _3$

  3. $n _1 > n _2 < n _3$

  4. $n _1 < n _2 > n _3$

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Correct Option: A
Explanation:

Frequency range of Y rays=${ n } _{ 1 }=>3\times { 10 }^{ 20 }㎐$

Frequency range of ultraviolet rays$={ n } _{ 2 }=7.5\times { 10 }^{ 14 }-3\times { 10 }^{ 17 }㎐$
So frequency of $\gamma$ rays $>$ frequency of ultraviolet rays
${ n } _{ 1 } >{ n } _{ 2 }$

The waves that are bent down by the ionosphere are

physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

  1. Ground waves

  2. Surface waves

  3. Direct waves

  4. Space waves

  5. Sky waves

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Correct Option: E
Explanation:

Sky wave propagation is that mode of wave propagation in which the radio waves emitted from the transmitting antenna reach the receiving antenna after reflection in the ionosphere.

The correct sequence of various regions in absorption spectrum is?

physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

  1. Ultraviolet, visible, infra-red, microwave

  2. Microwave, visible, infra-red, X-rays

  3. Infra-red, gamma rays, ultraviolet, microwave

  4. Visible, ultraviolet, microwave, infra-red

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Correct Option: A
Explanation:

Absorption spectrum is inversly proportional to the wavelength of the wave.

So, the correct sequence will be Ultraviolet, visible, infra-red, microwave as ultraviolet has maximum wavelength and microwave have least wavelength.

The transverse nature of electromagnetic radiation is demonstrated by.

physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

  1. Interference experiment

  2. Diffraction experiment

  3. Polarisation experiment

  4. Optical activity experiment

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Correct Option: C
Explanation:

The transverse nature of electromagnetic radiation is demonstrated by polarisation experiment.

The electron in hydrogen atom in a sample is in $n^{th}$ excited state, then the number of different spectrum lines obtained in its emission spectrum will be:

physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

  1. $1 + 2 + 3 + ..... + (n - 1)$

  2. $1 + 2 + 3 + ..... + (n)$

  3. $1 + 2 + 3 + ..... + (n + 1)$

  4. $1$ x $2$ x $3$ x ..... x $(n - 1)$

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Correct Option: A

Which of the following has maximum energy ?

physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

  1. radio waves

  2. X rays

  3. light waves

  4. micro waves

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Correct Option: B

A cube of size 10 cm is floating in equilibrium in a tank of water. When a mass of 10 gm is placed on the cube, the depth of cube inside water increases by $\mathrm { g } = 10 \mathrm { m } / \mathrm { s } ^ { 2 }$ density of water $= 1000 \mathrm { kg } / \mathrm { m } ^ { 3 } )$

physics upthrust in fluids, archimedes' principle and floatation applications of floatation principle of floatation and its applications when do objects float on water?

  1. 0.1 m

  2. 1 mm

  3. 1 m

  4. 0.31 m

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Correct Option: B
Explanation:

Let $x$ be the initial depth upto which the cube is sinked in water.

Let $d$ be the density of the cube
Then
$x\times 10 \times 10\times 1 \times g$
$=10\times 10 \times 10\times 1 \times g\times d$........(1) 
$\Rightarrow x=10d$
Let $x^1$ be the new depth, then 
$x^1\times 100 \times g=1000\times d \times g+10g$........(2)
subtracting (1) and (2) we get
$\Rightarrow 100x^1=10x+10$
$x^2-x= \frac{1}{10cm}=1mm$
Hence,
option $B$ is correct answer.