Assume that a radio station is about 200 ~km away from your location and the station operates at 972 kHz . How long does it take for an electromagnetic signal to travel from the station to you and how many wave crests

Correct answer: A. 666 μ s and 9.72 × 10^5 crests per second Time taken by wave to travel = 200 ~km 3 × 10^5 ~km ~s^ -1 =6.667 × 10^ -4 ~s 666 μ s Number of crests per second = Frequency Frequency =972 kHz=9.72 × 10^5 ~Hz There are 9.72 × 10^5 crests per second.

AIIMS 201827 May

Exam: AIIMS
Year: 2018
Date: 27 May
Subject: Physics
Chapter: Electromagnetic Waves

AIIMS 2018 · 27 May · Physics · Electromagnetic Waves

Assume that a radio station is about 200 ~km away from your...

Assume that a radio station is about

200 \mathrm{~km}

away from your location and the station operates at

972 \mathrm{kHz}

. How long does it take for an electromagnetic signal to travel from the station to you and how many wave crests does it send out per second?

Options

A $666 \mu \mathrm{s}$ and $9.72 \times 10^5$ crests per second
B $666 \mu \mathrm{s}$ and $972 \times 10^5$ crests per second
C $555 \mu$ s and $97.2 \times 10^7$ crests per second
D $555 \mu \mathrm{s}$ and $0.972 \times 10^5$ crests per second

Correct answer

A. $666 \mu \mathrm{s}$ and $9.72 \times 10^5$ crests per second

Step-by-step solution

Time taken by wave to travel

=\frac{200 \mathrm{~km}}{3 \times 10^5 \mathrm{~km} \mathrm{~s}^{-1}}=6.667 \times 10^{-4} \mathrm{~s} \approx 666 \mu \mathrm{s}

Number of crests per second = Frequency Frequency

=972 \mathrm{kHz}=9.72 \times 10^5 \mathrm{~Hz}

\therefore \quad

There are

9.72 \times 10^5

crests per second.

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