Waves 2

Specular reflection

Reflection of waves from a smooth surface in a definite direction.

Diffuse reflection

Reflection of waves from a rough surface in many different directions.

What are the three things that lie in the same plane according to the law of reflection?

The incident ray, reflected ray, and normal to the boundary.

What is the law of reflection?

The angle of incidence is equal to the angle of reflection.

What is the angle of incidence (θi)?

The angle between the incident ray and the normal.

What is the angle of reflection (θr)?

The angle between the reflected ray and the normal.

If the angle of incidence is 30°, what is the angle of reflection?

30°.

Why are the angles of incidence and reflection measured from the normal instead of the surface?

Because the law of reflection defines both angles relative to the normal, which is perpendicular to the surface.

What happens to the reflected ray when the angle of incidence increases?

The angle of reflection increases by the same amount.

If the incident ray makes a 60° angle with the surface, what is the angle of incidence?

30°, because the normal is perpendicular to the surface.

What happens to the speed of light when it travels from one medium to another?

Its speed changes, but its frequency remains constant.

What is the index of refraction (n)?

The ratio of the speed of light in a vacuum to its speed in a medium.

What is the formula for the index of refraction?

n = c/v

What does c represent in the index of refraction formula?

The speed of light in a vacuum.

What does v represent in the index of refraction formula?

The speed of light in a medium.

What is the approximate speed of light in a vacuum?

3.0 × 10⁸ m/s.

What does an index of refraction greater than 1 indicate?

Light travels slower in the medium than in a vacuum.

What happens to the speed of light as the index of refraction increases?

The speed of light in the medium decreases.

What is the relationship between the index of refraction and wave speed?

They are inversely proportional.

What happens to wave speed in an optically denser medium?

Wave speed decreases.

What happens to the index of refraction when wave speed decreases?

The index of refraction increases.

What is the relationship between optical density and the index of refraction?

An optically denser medium has a higher index of refraction.

Which has a higher index of refraction: a medium where light travels faster or slower?

The medium where light travels slower.

If the index of refraction increases, what happens to the speed of light in the medium?

The speed of light decreases.

What is total internal reflection?

The complete reflection of a wave back into its original medium instead of being refracted into the second medium.

What is the critical angle (θc)?

The angle of incidence at which the angle of refraction is 90°.

What happens to the refracted ray when the critical angle is reached?

It travels along the boundary between the two media at 90° to the normal.

When does total internal reflection occur?

When the angle of incidence is greater than the critical angle (θi > θc).

What must happen for total internal reflection to occur?

The wave must travel from a higher-index medium to a lower-index medium, and the angle of incidence must exceed the critical angle.

What happens when the angle of incidence is less than the critical angle?

The wave refracts into the second medium.

What happens when the angle of incidence equals the critical angle?

The angle of refraction is 90°.

How do endoscopes use total internal reflection?

Fiber-optic bundles guide light through repeated total internal reflections to illuminate and visualize internal body cavities.