Light is incident on aplane mirror at an angle of 46 degrees relative to its surface. What is the angle of reflection?

Your exact answer here:
http://en.wikipedia.org/wiki/Reflection_%28physics%29

The angle of incidence equals the angle of reflection but these are relative to the normal. Geometry will tell you what the angle relative to the surface is. Be specific about what you don't understand if you repost still don't get it.
http://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/refln/u13l2c.html

what is the frequency of threshold of pain _____ hz

To determine the angle of reflection in this scenario, we need to understand that the angle of incidence is equal to the angle of reflection. However, these angles are measured relative to the normal, which is an imaginary line perpendicular to the surface of the mirror.

In this case, the angle of incidence is given as 46 degrees relative to the mirror's surface. Since the angle of reflection is equal to the angle of incidence, the angle of reflection in this case is also 46 degrees relative to the mirror's surface.

Now, moving on to your next question about the frequency of the threshold of pain. The threshold of pain refers to the level of sound intensity at which sound becomes painful to the human ear. The frequency at this threshold can vary among individuals, but it is generally around 20,000 Hz or higher.

It's worth noting that sound frequency is measured in Hertz (Hz), which represents the number of cycles per second. The higher the frequency, the higher the pitch of the sound.