Physics Lab worksheet on refraction of light, another example of a physics Lab worksheet, based on guided discovery approach.

1. Page 1 of 5
Class: Grade 10 Physics Lab worksheet Mark:
Name: Subject: Refraction of light
Experiment 1
Refraction of light
Materials:
- Ray box or laser source
- Semi-cylindrical glass or transparent plastic piece
- Graduated disk
Procedure:
- Place the semi-cylindrical glass (or plastic piece) such
that its plane surface coincides with the diameter of the
graduated disk, as shown in the adjacent figure.
- Use the ray box or a laser source to direct a thin beam
of light obliquely on the plane surface of the semi-
cylindrical piece as in the figure. Adjust the beam to
graze the surface of the disk, and hits the semi-
cylindrical piece at its center.
1.1. What happened to the ray upon passing from the
semi-cylindrical piece to air? What do we call this
phenomenon?
…………………………………………………………………………………………………………………….…………………………………
- Observe the reflected part of light on the plane surface and the emerged part, which is bent upon
entering the semi-cylindrical piece.
1.2. Compare the intensity of the reflected ray and that of the incident ray.
…………………………………………………………………………………………………………………….…………………………………
1.3. Do you conclude that the reflection total or partial?
…………………………………………………………………………………………………………………….…………………………………
- We call the angle between the normal and the incident ray the angle of incidence i1, the angle
between the normal and the refracted ray the angle of refraction i2, and the angle between the normal
and the reflected ray the angle of reflection r.
1.4. Measure the angle of incidence i1, the angle of refraction i2 and the angle of reflection r.
…………………………………………………………………………………………………………………….…………………………………
1.5. Compare the angle of incidence i1 with the angle of reflection r
…………………………………………………………………………………………………………………….…………………………………
1.6. Compare the angle of incidence i1 with the angle of refraction i2
…………………………………………………………………………………………………………………….…………………………………
Incident
ray
i1
Normal
Normal
i2
Refracted
ray
Partially
reflected
ray
r

2. Page 2 of 5
1.7. Send the incident ray perpendicularly to the plane surface of the semi-cylindrical piece and
observe the refracted ray. What is the angle of incidence i1 and the angle of refraction i2 in this case?
What do we call this case?
…………………………………………………………………………………………………………………….…………………………………
1.8. Vary the angle of incidence several times. Does the beam always refract towards the normal or
away from the normal?
…………………………………………………………………………………………………………………….…………………………………
1.9. From what medium to what medium is light passing in this experiment?
…………………………………………………………………………………………………………………….…………………………………
1.10. Now reverse the direction of propagation of light. From what medium to what medium is light
passing now?
…………………………………………………………………………………………………………………….…………………………………
1.11. Vary the angle of incidence several times. Does the beam always refract towards the normal or
away from the normal?
…………………………………………………………………………………………………………………….…………………………………
…………………………………………………………………………………………………………………….…………………………………
1.12. Knowing that the medium in which light refracts towards the normal is said to be more refractive
medium. While the medium in which light refracts away from the normal is said to be less refractive.
What do you conclude from this experiment?
…………………………………………………………………………………………………………………….…………………………………
…………………………………………………………………………………………………………………….…………………………………
…………………………………………………………………………………………………………………….…………………………………
…………………………………………………………………………………………………………………….…………………………………
Experiment 2
Snell’s law
Materials:
- As in experiment 1
Procedure:
- What is the index n2 of the material that the semi-cylindrical piece is made of? (Ask the lab assistant
for it)
…………………………………………………………………………………………………………………….…………………………………
- The index of air is approximately equal to 1 (n2 = 1).
- Repeat experiment 1 several times by changing the angle of incidence i1 and record in each time the
angle of incidence i1 and the angle of refraction i2. Record the results in the table below. For each
measurement of i1 and i2, calculate sin(i1) and sin(i2). For each measurement, calculate the ratio
𝑠𝑖𝑛 𝑖2
𝑠𝑖𝑛 𝑖1
.
Record the results in the table below.

3. Page 3 of 5
Angle of incidence: i1
Angle of refraction (in air) i2
sin i1
sin i2
𝑠𝑖𝑛 𝑖2
𝑠𝑖𝑛 𝑖1
2.1. What do you notice for the ratio
𝑠𝑖𝑛 𝑖2
𝑠𝑖𝑛 𝑖1
?
…………………………………………………………………………………………………………………….…………………………………
2.2. Calculate the ratio
𝑛2
𝑛1
. What do you obtain?
…………………………………………………………………………………………………………………….…………………………………
2.3. Knowing that the incident ray, the refracted ray graze the surface of the graduated disk, and the
normal is also on the graduated disk, can we say that they lie in one plane?
…………………………………………………………………………………………………………………….…………………………………
2.4. Conclude the two laws of refraction
…………………………………………………………………………………………………………………….…………………………………
…………………………………………………………………………………………………………………….…………………………………
…………………………………………………………………………………………………………………….…………………………………
…………………………………………………………………………………………………………………….…………………………………
Experiment 3
Total internal reflection
Materials:
- As in experiment 1
Procedure:
- The same setup of experiment 1
- Use the source of light to direct a thin beam of light
perpendicular to the cylindrical surface (towards its
center) as in the adjacent figure.
- Rotate the source around the glass so that the angle
of incidence increases.
3.1. Is the angle of refraction (in air) always larger
than the angle of incidence (in glass or plastic)?
……………………………………………………………………
3.2. Keep increasing the angle of incidence until the angle of refraction becomes 90 as in the figure
below (in that case, the refracted ray is grazing the surface)
3.3. Record the corresponding angle of incidence i1
Incident
ray
i1
Normal
Normal
i2
Refracted
ray
Partially
reflected
ray

4. Page 4 of 5
…………………………………………………………………………………………………………………….…………………………………
3.4. This angle of incidence corresponding to an angle of refraction 90 is called the critical angle 
- Increase the angle of incidence i1 a little further
3.5. What do you observe?
…………………………………………………………………………………………………………………….…………………………………
…………………………………………………………………………………………………………………….…………………………………
3.6. Conclude
…………………………………………………………………………
…………………………………………………………………………
3.7. Record the corresponding angle of the reflected
ray
………………………………………………………………………………
3.8. Compare it to the angle of incidence
………………………………………………………………………………
3.9. Apply Snell's law to find sin, and then to find 
………………………………………………………………………………
………………………………………………………………………………
………………………………………………………………………………
…………………………………………………………………………………………………………………….…………………………………
Experiment 4
Refraction from a medium of smaller index to a medium of greater index
Materials:
- As in experiment 1
Procedure:
- The same setup of experiment 1.
- Use the source of light to direct a thin beam of
light in air towards the plane surface of the semi-
cylindrical piece towards its center, as shown in
the adjacent figure.
- Start with normal incidence (i1 = 0) and
gradually increase the angle of incidence i1.
4.1. Compare the angle of incidence i1 to the
angle of refraction i2. Which is greater?
………………………………………………………………………
…………………………………………………………………………………………………………………….…………………………………
Incident
ray

Normal
Normal
i2=90
Refracted
ray
Partially
reflected
ray
Incident
ray
i1
Normal
Normal
i2
Refracted
ray
Partially
reflected
ray

5. Page 5 of 5
4.2. Does the beam always refract towards the normal or away from the normal?
…………………………………………………………………………………………………………………….…………………………………
4.3. Can we obtain total internal reflection? Can we find the critical angle?
…………………………………………………………………………………………………………………….…………………………………
4.4. Conclude
…………………………………………………………………………………………………………………….…………………………………
…………………………………………………………………………………………………………………….…………………………………
Experiments 5
Dispersion of white light using a prism
Materials:
- Glass or plastic prism
- White light source
- Screen
Procedure:
- Intercept the path of the light beam issued by the white light source with the prism, as in the figure
above.
- Tilt the prism until the light beam emerges from the other face of the prism as a band of colored light
rays at different angles.
- Intercept the emerged rays with a screen so that you can observe the colors ranging from red to
violet.
5.1. What do we call this band of colors?
…………………………………………………………………………………………………………………….…………………………………
5.2. What do we call this phenomenon?
…………………………………………………………………………………………………………………….…………………………………
- Let us compare the bending of two rays contained in the beam of white light: the red and the violet
ray:
5.3. Which one of them has a greater angle of refraction? And which has the less angle of refraction?
…………………………………………………………………………………………………………………….…………………………………
5.4. Knowing that the red color has larger wavelength than violet color, can you deduce a link between
the angle of refraction to the wavelength?
…………………………………………………………………………………………………………………….…………………………………
5.6. Can you deduce whether the index of refraction of the prism increases or decreases with
increasing wavelength of the light passing through it?
…………………………………………………………………………………………………………………….…………………………………
…………………………………………………………………………………………………………………….…………………………………