You are traveling in a spaceship at a speed of 0.70c away from earth. you send a laser beam toward the earth traveling at velocity c relative to you.
what do observers on the earth measure for the speed of the laser beam?

The speed of the light for the observers on the Earth appears to be moving towards the Earth.

Further Explanation:

The speed of the laser beam coming from the spaceship moving away from the Earth at the speed comparable to the speed of light is given by the Einstein’s theory of relativity.

According to the Einstein’s theory, the relative speed observed from the Earth is given as:

                 ......(1)

Here, is the speed of light for the observer on the Earth, is the relative speed of the light observed from the spaceship,    is the speed of the spaceship, is the speed of the laser beam and is the speed of the light.

The relative speed of the light as observed from the spaceship moving away from Earth is:

Substitute the values of and in above expression.

Now, substitute the value of in equation (1).

The negative sign shows that the beam is moving opposite to the direction of motion of the spaceship.

Thus, the speed of the light for the observers on the Earth appears to be moving towards the Earth.

Learn More:

1. What is the frequency of light for which the wavelength is 7.1 × 102 nm

2. Calculate the frequency of the red light emitted by a neon sign with a wavelength of 690 nm

3. Which of the following statements about electromagnetic radiation is truehttps://

Answer Details:

Grade: High School

Subject: Physics

Chapter: Speed of light

Keywords:

Spaceship, speed of 0.7c, laser beam, towards the Earth, theory of relativity, relative speed, observer, moving away from Earth, Earth, speed of light.

c. newton's third law of motion