Answer:
Change the wavelength to half while keeping velocity constant or change the wave velocity to 2 times while keeping wavelength constant.
Explanation:
The frequency of a wave can be defined as the rate of change of wave speed with respect to the wavelength of the wave.
Mathematically,

Here, v is the velocity, lambda is the wavelength, and f is the frequency of the wave.
If the observer want to double the frequency of the wave, then he should increase the wave velocity two times and take wavelength constant for this case or either he should half the wavelength of the wave to take the velocity of the wave constant.
75
p = w / t
p = 180 / 2.4
p = 75
Answer:
I believe it's 2) sound waves
Explanation:
With sound waves, the energy travels along in the same direction as the particles vibrate. This type of wave is known as a longitudinal wave, so named because the energy travels along the direction of vibration of the particles.
Answer:
B. -2
Explanation:
The total charge on an atom is the sum of all individual charges present in it. Therefore, the total charge on this atom is given by the following formula:

where,
q = total charge on atom = ?
= no. of protons in the atom = 15
= no. of electrons in the atom = 17
= no. of neutrons in the atom = 12
= charge on proton = +1
= charge on electron = -1
= charge on neutron = 0
Therefore,

Hence the correct option is:
<u>B. -2</u>
Approximately 15 m/s is the speed of the car.
<u>Explanation:</u>
<u>Given:</u>
speed of sound - 343 m/s
You detect a frequency that is 0.959 times as small as the frequency emitted by the car when it is stationary. So, it can be written as,


If there is relative movement between an observer and source, the frequency heard by an observer differs from the actual frequency of the source. This changed frequency is called the apparent frequency. This variation in frequency of sound wave due to motion is called the Doppler shift (Doppler effect). In general,

Where,
- Observed frequency
f – Actual frequency
v – Velocity of sound waves
– Velocity of observer
- velocity of source
When source moves away from an observer at rest (
), the equation would be



By substituting the known values, we get






Approximately 15 m/s is the speed of the car.