Refraction of light Flashcards
Define ‘normal’ in the context of refraction.
The normal is an imaginary line drawn perpendicular to the boundary at the point where the light ray enters or exits the medium.
Define ‘angle of incidence’ in the context of refraction.
The angle of incidence is the angle between the incident ray and the normal at the boundary of two media.
Define ‘angle of refraction’.
The angle of refraction is the angle between the refracted ray and the normal at the boundary of two media.
State the formula for refractive index in terms of angles of incidence and refraction.
Refractive index (n) = sin(i) / sin(r), where i is the angle of incidence and r is the angle of refraction.
Describe how to calculate the refractive index using experimental data.
Measure the angles of incidence and refraction using a protractor, then apply the formula n = sin(i)/sin(r) to calculate the refractive index.
Describe an experiment to show the refraction of light by transparent blocks of different shapes.
- Place a transparent block (e.g., rectangular or triangular prism) on a sheet of paper. 2. Shine a ray of light at an angle onto the block. 3. Trace the incident and refracted rays. 4. Measure the angles of incidence and refraction. 5. Repeat with blocks of different shapes and observe the bending of light.
Alternate-style question: How can you ensure accuracy when tracing light rays in a refraction experiment?
Use a narrow light ray, ensure the block is stationary, and trace the rays carefully before removing the block.
Define the term ‘critical angle’.
The critical angle is the angle of incidence in a denser medium above which total internal reflection occurs when light moves to a less dense medium.
Define ‘total internal reflection’.
Total internal reflection is the complete reflection of light within a denser medium when the angle of incidence exceeds the critical angle.
State the formula for the critical angle in terms of the refractive index.
Critical angle (c) is given by sin(c) = 1/n, where n is the refractive index of the denser medium.
Describe an experiment to demonstrate total internal reflection.
- Use a semi-circular glass block. 2. Shine a light ray toward the flat surface at increasing angles. 3. Observe that at a certain angle (the critical angle), the refracted ray disappears, and all light reflects internally.
Alternate-style question: How can you identify the critical angle experimentally?
Increase the angle of incidence gradually and observe when the refracted ray just disappears, marking the onset of total internal reflection.
Describe the use of optical fibres in telecommunications.
Optical fibres use total internal reflection to transmit light signals over long distances with minimal loss, enabling high-speed communication.
State the advantages of optical fibres in telecommunications.
- High data transfer rates, 2. Minimal signal loss, 3. Immunity to electromagnetic interference, 4. Lightweight and flexible.
Describe an experiment to observe the refraction of light through a triangular prism.
- Place a triangular prism on a sheet of paper. 2. Shine a light ray into one face of the prism. 3. Trace the incident, refracted, and emergent rays. 4. Observe how the light bends inside the prism and emerges at an angle.
