At the solution of tasks most often it is necessary to find a hade of the light beam and a subject thrown horizontally or at an angle to the horizon. The hade of a beam is by means of construction or simple calculations when the angle of reflection or refraction is known. The hade of a body is in calculation result.

## It is required to you

- - protractor;
- - range finder;
- - table of absolute measures of refraction.

## Instruction

1. When falling a light beam on a flat surface restore a perpendicular to it in a falling point by means of a protractor, the square or the angle meter. The corner between a perpendicular and the falling beam will also be a hade. If the surface is not the plane, in a point of falling of a beam construct a tangent, and lower a perpendicular to a tangent in this point. Define a corner as well as in the previous case. In both cases for measurement of a corner use a protractor or the angle meter.

2. If the angle of reflection is known, then under the first law of reflection of light beams it will be equal to a hade. When the angle of refraction on border of two environments is known, find a relative indicator of their refraction from the table or calculate it, using absolute measures. Then increase this indicator by a refraction sine of the angle. The sine of the angle of falling of a light beam of Sin(α) =n will be result • Sin(β). By means of the engineering calculator or special tables find value of a hade, having used function of an arcsine.

3. Measure a hade of a body, having restored a perpendicular in a falling point, it is a corner between a perpendicular and the direction of final speed of a body. When the body is thrown at an angle to the horizon which is in advance known, the hade is equal 90º minus a corner under which the body is thrown.

4. In case the body is thrown horizontally from some height, measure distance at which the body will fall to the ground and height from which it was dumped in meters. Make it by means of a roulette or from a range finder. To find a hade, divide distance which overcame a body on the doubled height from which it fell. It will be a falling tangent of angle. Find a corner by means of the calculator or the table.

5. In these calculations resistance of air which can be neglected at small speeds with which bodies, for example, the thrown stone move is not considered. At the big resistance of the environment at increase in speed the results will change.