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Light Spectrum

The speed of ...

Question

The speed of electromagnetic waves in air is ___________.

2 \times 10^{5}

km/s

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2 \times 10^{6}

km/s

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2 \times 10^{7}

km/s

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2 \times 10^{8}

km/s

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Solution

The correct option is C $2 \times 10^{5}$ km/s
Speed of $E M$ waves in $3 \times 10^{5} k m / s e c o n d$ .
While traveling in other media, such as air the speed of $E M$ waves gets slower due to change in wavelength and in all their options only one option is there
i.e $2 \times 10^{5} k m / s$ less than $3 \times 10^{5} k m / s e c o n d$ .

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Four molecules of gas have speeds $1, 2, 3$ and $4 k m s^{- 1}$ . The value of the root mean square speed of the gas molecule is

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400 k g

3600 k m

(R = 6400 k m) (g_{o} = 10 m / s^{2})

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