Question

12. a) Sound waves travel at a speed of 340 m s¹ in air

at 20°C. If the frequency of these waves is 2.5 kHz,
what is their wavelength?
b) Infra-red electromagnetic waves travel at a
speed of 3.0 x 108 m s¹. Calculate the frequency of
these waves if their wavelength is 1.2 x 10-6 m.

Answer 1

`a)0.136m \\ b)2.5 * 10 {}^(14) cycle \: per \: sec`

Step-by-step explanation:

Greetings!!

Let's start from question a

Given values :-

speed(velocity)= 340m/s

frequency=2.5kHz

Temperature= 20°c

required values:-

wave length=?

solution:-

Firstly, recall velocity-wavelength equation

v=λf,

substitute known variables into the equation

• (340)= (2500). λ

To not get confused 2500 comes when kHz is changed to Hz. (notice)

solve for wavelength

• λ= 0.136m

for the second question b. also use the same procedure and the same format ( formula)

Thus, we work as

Given values:-

speed(velocity)= 3.0×10^8

wavelength=12×10^-6

required values:-

frequency=?

solution:-

Firstly, recall velocity-wavelength equation

• v=λf

substitute known values into the equation

(3.0×10^8)= f(1.2×10^-6)

solve for frequency

f= 2.5× 10^14 Hz

If any questions or anything else tag me on comments.

Hope it helps!!!