71.

A dim star of magnitude + 14.5 explodes into a nova of magnitude + 2. The factor by which the brightness of the star has increased is

• 12.5

• 10²

• 10⁵

• 10⁴

If the sun becomes twice as hot

• the output of radiated energy will be eight times larger

• it will radiate predominantly in the infrared

• it will radiate predominantly in the ultraviolet

• the output of the radiated energy will be eight times smaller