In the past, asteroids striking the earth have produced disastrous results. If we discovered an asteroid on a collision course with the earth, we could, in principle, deflect it and avoid an impact by focusing a laser on the surface. Intense surface heating from the laser could cause surface material to be ejected into space at high speed. Required:
How would this deflect the asteroid?

Explained below.

Explanation:

We are told that the surface material is ejected into space at a high speed. This means that it will have a likely high momentum as well.

Now, we can say that the total momentum is conserved because the entire asteroid system behaves like an isolated system.

Also, as the surface material is moving with the high momentum like we established earlier, it will cause the asteroid to move with a speed in an opposite direction which also means deflection in an opposite direction.

wavelength divides in half and speed stays the same.