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Multiple choice physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

PAR range of wavelength is 

  1. $400-700 nm$

  2. $400-800 nm$

  3. $450-950 nm$

  4. $500-600 nm$
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

Multiple choice physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

Electromagnetic waves that include light belong to

  1. light spectrum.

  2. electronic spectrum.

  3. electromagnet group.

  4. electromagnetic spectrum.
Reveal answer Fill a bubble to check yourself
D Correct answer
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.

Multiple choice physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

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

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

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

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

  4. $n _1 < n _2 > n _3$
Reveal answer Fill a bubble to check yourself
A Correct answer
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
${ n } _{ 1 } >{ n } _{ 2 }$

Multiple choice physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

The correct sequence of various regions in absorption spectrum is?

  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
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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 $= 1000 \mathrm { kg } / \mathrm { m } ^ { 3 } )$

  1. 0.1 m

  2. 1 mm

  3. 1 m

  4. 0.31 m
Reveal answer Fill a bubble to check yourself
B Correct answer
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.