3.9 Refraction at a plane surface

• Refraction is the bending of waves as they pass from one medium to another due to a change in wave speed
• Order the steps involved when light passes from air to glass:

  1️⃣ Light enters air

  2️⃣ Light reaches the air-glass boundary

  3️⃣ Wave speed decreases

  4️⃣ Wavelength decreases

  5️⃣ Light bends towards the normal
• What is the angle of refraction when light passes from air ($n_{1} =$$1$) to glass ($n_{2} =$$1.5$) at an angle of incidence of $\theta_{1} =$$30^\circ$?


  $19.5^\circ$
• Order the factors influencing refraction from most to least significant:

  1️⃣ Refractive index difference

  2️⃣ Angle of incidence

  3️⃣ Frequency
• Snell's Law is represented by the formula $n_{1} \sin \theta_{1} =$$n_{2} \sin \theta_{2}$


  True
• The formula to calculate the refractive index of medium 2 is $n_{2} =$$\frac{n_{1} \sin \theta_{1}}{\sin \theta_{2}}$


  True
• Light passes from air to glass with $\theta_{1} =$$30^\circ$ and \theta_{2} = 20^\circ</latex>. The refractive index of glass is approximately 1.46
• In reflection, the angle of reflection is equal to the angle of incidence
• In a denser medium, the wave speed decreases and the wavelength decreases.


  True
• Snell's Law relates the refractive indices and angles of incidence and refraction when a wave passes from one medium to another.
• Higher refractive index differences cause more pronounced bending of waves.
• Snell's Law relates the refractive indices and angles of incidence and refraction when a wave passes from one medium to another.
• Match the variable with its description:

  $n_{1}$ ↔️ Refractive index of medium 1

  $\theta_{1}$ ↔️ Angle of incidence

  $n_{2}$ ↔️ Refractive index of medium 2

  $\theta_{2}$ ↔️ Angle of refraction
• If we know the refractive index of one medium and the angles of incidence and refraction, we can use Snell's Law to calculate the refractive index of the other medium
• When light passes from air to glass, the angle of refraction is greater than the angle of incidence.

  False
• Refraction occurs when a wave passes from one medium to another with the same density.

  False
• Match the medium with its effect on wave speed and wavelength:

  Denser medium ↔️ Decreases speed and wavelength

  Less dense medium ↔️ Increases speed and wavelength
• The formula for Snell's Law is $n_{1} \sin \theta_{1} =$$n_{2} \sin \theta_{2}$


  True
• Changes in frequency affect wave speed and direction, influencing the angle of refraction.


  True
• Snell's Law relates the refractive indices and angles of incidence and refraction
• To determine the refractive index of an unknown medium, we can rearrange Snell's Law to solve for $n_{2}$
• Steps to use Snell's Law for calculations:

  1️⃣ Identify given variables

  2️⃣ Apply the formula

  3️⃣ Rearrange and solve for the unknown variable
• Match the feature with the correct phenomenon:

  Direction Change ↔️ Waves bend into a different medium (Refraction)

  Medium Involvement ↔️ Two media needed (Refraction)

  Wave Properties ↔️ Wave speed changes (Refraction)
• Match the property with the correct phenomenon:

  Wave Speed ↔️ Unchanged in reflection

  Wavelength ↔️ Changes in refraction

  Bending ↔️ No bending in reflection

  Examples ↔️ Light reflecting off a mirror (Reflection)