Keywords: IGCSE Prescribed Practical, Refractive Index, Glass, Angle of Refraction, Physics, Snell’s Law, Angle of Incidence, Light Ray, Glass Block, Optics

Introduction: In this IGCSE Prescribed Practical experiment, we will measure the angle of refraction of a ray of light passing through a glass block to calculate its refractive index. The refractive index is a measure of how much a medium slows down light compared to its speed in a vacuum. By understanding the refractive index of materials, we can explore the principles of optics and the behavior of light as it travels through different media.

Equipment Needed:

Glass block Ray box or laser pointer White paper Protractor Pencil Ruler Step by Step Method:

• Place the glass block on the white paper and trace its outline using a pencil.
• Position the ray box or laser pointer so that it shines a light ray onto one side of the glass block at an angle, ensuring that the light ray passes through the glass block and exits on the opposite side.
• Trace the path of the incident light ray and the refracted light ray on the white paper using a pencil.
• Remove the glass block and extend the traced rays using a ruler to form two lines that intersect.
• Measure the angle of incidence (i), which is the angle between the incident ray and the normal (a line perpendicular to the glass surface).
• Measure the angle of refraction (r), which is the angle between the refracted ray and the normal.
• Use Snell’s Law to calculate the refractive index (n) of the glass: n = sin(i) / sin(r)

Expected Findings and Calculations: By measuring the angle of incidence (i) and the angle of refraction (r), we can calculate the refractive index (n) of the glass using Snell’s Law. The refractive index is a property of the material that influences how light travels through it.

Snell’s Law formula: n = sin(i) / sin(r)

Conclusion: By performing this IGCSE Prescribed Practical experiment, you will be able to determine the refractive index of glass. Understanding the refractive index is essential for studying optics and the behavior of light in different media, which has numerous applications in physics and engineering.

Questions:

1. What is the refractive index?
2. How do you measure the angle of incidence and the angle of refraction?
3. What is Snell’s Law?
4. Why do we use a glass block in this experiment?
5. What are some applications of understanding the refractive index in real life?

Answers:

1. The refractive index is a measure of how much a medium slows down light compared to its speed in a vacuum.
2. The angle of incidence is measured between the incident ray and the normal (a line perpendicular to the glass surface), and the angle of refraction is measured between the refracted ray and the normal.
3. Snell’s Law states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is equal to the refractive index: n = sin(i) / sin(r).
4. We use a glass block in this experiment because it is a transparent medium with a known refractive index, allowing us to easily observe the behavior of light as it passes through.
5. Understanding the refractive index has numerous applications, including the design of optical devices such as lenses, prisms, and fiber optics, as well as in fields such as astronomy and telecommunications.

• Practical Physics