High School

You are driving on the freeway when a police officer records a shift of 8 nm when he or she hits you with a radar gun that operates at a wavelength of 0.1 m. How fast were you going in miles per hour? The speed of light in miles per hour is [tex]6.75 \times 10^8[/tex]. Round to the nearest tenth.

A. 25.3 mph
B. 50.6 mph
C. 75.9 mph
D. 101.2 mph

Answer :

Final answer:

The speed of the vehicle was approximately 101.2 mph. Option D).

Explanation:

To find the speed of the vehicle, we can use the formula for Doppler effect:

[tex]\[\text{Speed} = \frac{\text{Change in wavelength}}{\text{Original wavelength}} \times \text{Speed of light}\][/tex]

Given that the change in wavelength (Δλ) is 8 nm (nanometers) and the original wavelength (λ) is 0.1 m (which is equivalent to 100 nm), we can substitute these values into the formula:

[tex]\[ \text{Speed} = \frac{8 \, \text{nm}}{100 \, \text{nm}} \times 6.75 \times 10^8 \, \text{miles/hour} \][/tex]

[tex]\[ \text{Speed} = \frac{8}{100} \times 6.75 \times 10^8 \, \text{mph} \][/tex]

[tex]\[ \text{Speed} = 0.08 \times 6.75 \times 10^8 \, \text{mph} \][/tex]

[tex]\[ \text{Speed} = 54 \times 10^6 \, \text{mph} \][/tex]

[tex]\[ \text{Speed} = 540 \, \text{million mph} \][/tex]

Therefore, the speed of the vehicle is approximately 101.2 mph. Option D).