Maria and carla were hiking when maria tripped, fell, and sprained her ankle. carla took out the first-aid kit and unwrapped a cold pack. carla popped a vial that was inside the cold pack. the two chemicals inside the pack mixed together and the pack began to get icy cold. carla applied the pack to maria's ankle. what kind of reaction occurred in the cold pack? what evidence supports your answer? question 11 options: a. it is a physical change because the substance in the vial dissolved in the pack's liquid. b. it is a chemical change because two different chemicals are mixed together. c. it is a chemical change because heat energy is absorbed and the pack gets colder. d. it is a physical change as evidenced by a drop in temperature.

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.