a ray of light strikes a plane mirror, such that angle with the mirror is 20 °. what is value of angle of reflection? what is the angle between the incident ray and the reflected ray?
Answers
the angle of reflection will be same as angle of incidence i.e 20° and angle between incident and reflected Ray will be 180° - 20° + 20° = 140°
Given,
When a ray of light strikes a plane mirror, then the angle it makes with the mirror = 20 °
To find,
a) The value of the angle of reflection
b) The angle between the incident ray and the reflected ray.
Solution,
We can simply solve this numerical problem by using the following process:
As per the principles of ray optics;
When a ray of light is falling on the surface of a mirror and gets reflected, then,
The angle of incidence = the angle of reflection,
where,
angle of incidence = angle between the incident ray and the median line
the angle of reflection = angle between the reflected ray and the median line
{Statement-1}
Now, according to the question;
For the incident ray of light,
the angle made with the mirror
= the angle between the incident ray of light and the mirror = 20°
=> the angle between the incident ray of light and the median = 90° - the angle between the incident ray of light and the mirror
(Since the median line is perpendicular to the mirror)
=> the angle between the incident ray of light and the median = angle of incidence = 90° - 20° = 70°
=> the angle between the reflected ray of light and the median = angle of reflection = 70°
(according to the statement-1)
Now,
The angle between the incident ray and the reflected ray
= the angle between the incident ray of light and the median + the angle between the reflected ray of light and the median
= angle of incidence + angle of reflection
= 70° + 70°
= 140°
Hence, the measure of the angle of reflection is equal to 70° and the measure of the angle between the incident ray and the reflected ray is equal to 140°, respectively.