what are the conditions under which light can be approximated as rays even though light is really a wave

The weights of bags filled by a machine are normally distributed with a standard deviation of 0.05 kilograms and a mean that can be set by the operator. at what level should the mean weight be set if it required that only 1% of the bags weigh less than 9.5 kilograms? round the answer to 2 decimal places.

The velocity of sound wave in air at 35°c is 353m/s, calculate the velocity of sound at 46°c

Derive the formula 2as=v² -u² where the formula have have usual meanings