Question

What is the frequency of radiation whose wavelength is 5.2×10⁻⁵ m ?

Express your answer using two significant figures.

ν =		s−1

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Part B

What is the wavelength of radiation that has a frequency of 2.8×10⁸ s−1 ?

Express your answer using two significant figures.

λ =		m

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Part C

Would the radiations with a wavelength 5.2×10⁻⁵ m or a frequency of 2.8×10⁸ s−1 be detected by an X-ray detector?

The radiation with a wavelength 5.2×10−5 m can be observed by an X-ray detector.

The radiation with a frequency of 2.8×108 s−1 can be observed by an X-ray detector.

Neither of the radiations with a wavelength 5.2×10−5 m or a frequency of 2.8×108 s−1 can be observed by an X-ray detector.

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Part D

What distance does electromagnetic radiation travel in 10.9 fs ?

Express your answer using three significant figures.

d =		m

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Answer 1

Ans. 1. Using, c = vl      , where, v (nu) = frequency, l (lambda) = wavelength and c= speed of EMR

            Also, c = 3 x 10⁸ ms^-1 (approx.)

Frequency, v = c/ l = 3 x 10⁸ ms^-1 / (5.2 x 10^-5 m)

            Or, v = 0.57692 x 10³ s^-1 = 5.7 x 10¹² s^-1  

Ans. 2. Wavelength, l = c / v = 3 x 10⁸ ms^-1 / (2.8 x 10⁸ s^-1) = 1.07 m

Ans. 3. The wavelength of of X-rays = 10^-10 to 10^-12. A X-ray detector detects EMR of this range only.

Since, neither of the given EMRs have wavelength in this range, none of them are detected by X-ray detector.

Correct option: C.

Ans. 4. 1 fs = 1 femtosecond = 10^-15 second

Speed of light = 3 x 10⁸ ms^-1

Distance travelled in 10.9 fs = 3 x 10⁸ ms^-1 x (10.9 x 10^-15 s)

                                    = 3.27 x 10^-6 m