what is the amount of light energy reflected back into space called?

Answer 1

The FRACTION of light reflected back to space is called the albedo. The radiation itself would just be called the reflected radiation.

Be careful when using the word "light". It properly refers only to visible radiation between 400 and 700 nm in wavelength. Much (roughly 1/3) of the energy received from the sun is not visible. "Albedo" usually includes the fraction of the invisible radiation that is reflected in the near infrared and ultraviolet.