Question

Police check your speed using a light source that operates at 900 nm. You are in...

Police check your speed using a light source that operates at 900 nm. You are in a car driving towards the officer at 78 mph. What is the wavelength and frequency of the light that is reflected from your car that the officer detects?

The wavelength of the reflected light is ____nm.

The frequency of the reflected light is ___Hz.

Homework Answers

Answer #1

Given the wavelength of light source = 900nm = 900 x 10-9m. If c is the velocity of light (c = 3 x 108m/s), the frequency of light source is

The listener (car) is approaching towards the source at a speed of v = 78mph = 34.87 m/s.

Taking the source to be at rest, the apparent frequency of light recieved by the car is given by

This is the frequency recieved by the car. Now this frequency is reflected back to the officer. Now the apparent frequency recieved by the officer is,

Here the apparent frequency and the source frequency are same. So the wavelength of the reflected light is 900nm.

Also the frequency of the reflected light is 3.33 x 1014Hz.

Know the answer?
Your Answer:

Post as a guest

Your Name:

What's your source?

Earn Coins

Coins can be redeemed for fabulous gifts.

Not the answer you're looking for?
Ask your own homework help question
Similar Questions
Problem 1: A police officer pulls over a physics student for running a red light. The...
Problem 1: A police officer pulls over a physics student for running a red light. The student tries to use the Doppler effect to get out of the ticket by telling the officer that since he was driving towards the light, the frequency was shifted and actually appeared green instead of red. What fraction of the speed of light would the student need to be traveling in order for this to actually occur? Assume the red light has a wavelength...
Doppler Effect: 1. A stationary police officer using a speed “radar detector” sends a signal with...
Doppler Effect: 1. A stationary police officer using a speed “radar detector” sends a signal with a frequency of 100,000 Hz. The speed of sound is 340 m/s. What is the wavelength of the (ultra) sound wave produced by the detector? The sound wave reflects off a vehicle moving toward the officer. How does the frequency of the reflected sound wave (as recorded by the detector) compare to the original sound wave? 2. The light waves from a distance start...
A light source of wavelength 504 nm is moving away from earth with speed u. The...
A light source of wavelength 504 nm is moving away from earth with speed u. The wavelength measured by an observer on earth is 651nm. Find u/c. (CORRECT ANSWER IS 0.250)
Slick Willy is in traffic court (again) contesting a $50.00 ticket for running a red light....
Slick Willy is in traffic court (again) contesting a $50.00 ticket for running a red light. “You see, your Honor, as I was approaching the light, it appeared yellow to me because of the Doppler effect. The red light from the traffic signal was shifted up in frequency because I was traveling towards it, just like the pitch of an approaching car rises as it approaches you.” Calculate how fast Slick Willy must have been driving, in meters per second,...
An ultrasound machine in a hospital uses a sound source at 5.10000MHz. Assuming that the speed...
An ultrasound machine in a hospital uses a sound source at 5.10000MHz. Assuming that the speed of the ultrasound in the body is same as water (1440 m/s), determine the wavelength in the body. If blood cells are moving towards the sound source at a speed of 0.8 m/s, at what frequency do the crests of the sound wave pass through the blood cell? What is the frequency of the sound waves reflected back towards the source by the blood...
You have a diffraction grating with 3000 lines/cm. You also have a light source that emits...
You have a diffraction grating with 3000 lines/cm. You also have a light source that emits light at 2 different wavelengths, 428 nm and 707 nm, at the same time. The screen for your experiment is 1.5 meters from the diffraction grating. A. What is the line spacing for the grating? B. What is the difference in the angle of the 2nd bright fringe for each wavelength for this grating? C. Which wavelength is closer to the center of the...
2. 1189 A police car is sounding a siren with 1340 Hz on a 20°C day....
2. 1189 A police car is sounding a siren with 1340 Hz on a 20°C day. Answers must be within 2 Hz of correct answer.        Part Description Answer Save Status A. You are standing beside the road. What frequency do you hear as the police car approaches you at 128 km/hr? (include units with answer) A: 1495 Hz C: 1494.97 Hz Hints: 0,0 # tries: 1 B. You are standing beside the road. What frequency do you hear after...
Your idiot friend won’t calm down. So the police officer fires her revolver in the air...
Your idiot friend won’t calm down. So the police officer fires her revolver in the air to get his attention. Then she blows over the top of the gun barrel to dispel the smoke coming from it. When she does this, you distinctly hear the fundamental mode of the gun barrel resonate at 1.352 kHz (you really have amazing hearing, by the way). (a) If we treat the gun barrel as a cylinder which is open at one end and...
Question: In your basement lab, you have set up a double-slit experiment. Your light source is...
Question: In your basement lab, you have set up a double-slit experiment. Your light source is monochromatic, with a wavelength of 486 nm. The slit spacing is 0.700 mm and the screen is set up 1.6 m from the slits. Find the distance along the screen between adjacent bright fringes. PLEASE SHOW ALL WORK, AN EXPLANATION, AND A DRAWING REPRESENTATION.
Monochromatic light of wavelength 477 nm from a distant source passes through a slit that is...
Monochromatic light of wavelength 477 nm from a distant source passes through a slit that is 0.0310 mm wide. In the resulting diffraction pattern, the intensity at the center of the central maximum (θ = 0∘) is 1.28×10−4 W/m2 . What is the intensity at a point on the screen that corresponds to θ = 1.20∘. Express your answer to three significant figures and include the appropriate units.
ADVERTISEMENT
Need Online Homework Help?

Get Answers For Free
Most questions answered within 1 hours.

Ask a Question
ADVERTISEMENT