Hi. I need help with this question :

A piece of copper of mass 40g at 200°C is placed in a copper calorimeter of mass 60g containing 50g of water at 25°C. Ignoring heat losses, what will be the final temperature of the mixture.
(Specific heat capacity of copper= 0.4J/g/K, specific heat capacity of water= 4.2J/g/K )?

Please show workings.

Antireflective coatings on solar cells are often made by applying a thin film of silicon nitride (sinx), which has an index of refractive of 1.2, on the top of the silicon solar cell, which has a refractive index of about 3.5. however, the sun emits radiation of various wavelengths which the solar cell absorbs, and the antireflective coating can only absolutely minimize the reflection of one of these wavelengths. the coating thickness is chosen to reduce the reflection of green/yellow light (e = 2.2 ev), which is the most intense color in the solar spectrum (shown below). which of the following coatings would minimize reflection of green/yellow light? the answer is 820 nm how? what is the angular width of the central maximum of an electron traveling at 2 x 108 m/s going through a single slit of width 1 mm.