Reflection of Light
1. The paper was secured at each of its edges to the pinboard using four thumbtacks.
2. A horizontal line was drawn across the center of the plain paper using a ruler. This
served as the mirror line.
3. A protractor was used to measure a ninety-degree angle at the center of the mirror
line.
4. A line approximately 5 cm long was extended from one side of the mirror line
using a ruler to represent this angle. This line was identified as the normal.
5. A 20° angle was measured from the left-hand side of the normal using a
protractor. This was recorded as the angle of incidence.
6. A straight line was drawn at this angle to the normal using a ruler. This line
touched the mirror line exactly at the point where the normal met it. One optical
pin was placed directly on this line.
7. The mirror was placed on the mirror line so that the center of its reflective side
aligned directly with the normal.
8. At eye level, the reflection of the pin was observed in the mirror from the opposite
side of the normal, relative to where the 20° line had been drawn.
9. A pin was placed on the paper directly in line with the image of the pin seen in the
mirror. This pin was identified as the image pin, I1.
10. A second pin was placed behind I1, directly in line with it. This was identified as
the second image pin, I2. The pins were aligned so that when viewed from behind
at eye level, only one pin was visible.
11. The image pins were removed, and a ruler was used to draw a line through the
holes made by I1 and I2 to the point where the normal met the mirror line.
12. The protractor was used to measure the angle formed by the line and the normal.
This was recorded as the angle of reflection.
13. Steps 5-12 were repeated, this time using angles of incidence of 40° and 60°.
14. The results were then tabulated.
Here are the answers to the questions based on the provided images:
1. What is reflection?
Reflection is the phenomenon where light bounces off a surface instead of passing
through it. When light strikes a reflective surface such as a mirror, it changes
direction while maintaining its speed and wavelength.
2. Give examples of everyday observations to support reflection.
Examples of everyday reflection taking place would be a person seeing themselves
in the mirror, representing the reflection of them and how they look. Another
example would be the reflection of trees and buildings in a still body of water.
3. What are the laws of reflection?
The two laws of reflection are:
The law of reflection defines that upon reflection from a smooth surface, the
angle of the reflected ray is equal to the angle of the incident ray, with respect
to the normal to the surface that is to a line perpendicular to the surface at the
point of contact.
The reflected ray is always in the plane defined by the incident ray and the
normal to the surface at the point of contact of the incident ray.
4. What does the line drawn represent, and what’s the significance of the arrows?
The line drawn in the diagram represents the reflecting surface of the plane
mirror. It acts as a reference for measuring angles of incidence and
reflection.
The arrows indicate the direction of light rays traveling from the object (pin
1) towards the mirror and then reflecting towards the observer's eye. This
helps demonstrate the path of light and how the image is perceived.
5. What are the possible sources of error and precautions taken to minimize them?
Possible sources of error: Possible sources of error may be the misalignment of
pins, leading to incorrect observations and parallax error when viewing pin images
from an incorrect direction (it should be read at eye level).
Precautions taken were to carefully align the pins in a straight line to ensure
accuracy and position the eye correctly to avoid parallax error.
