1. **Problem Statement:** Explain the concepts of total internal reflection, refraction, and reflection with examples using air-aluminium and air-glass boundaries. Also, state two common properties of all waves. 2. **Total Internal Reflection:** This occurs when a wave traveling from a medium with a higher refractive index to a lower refractive index hits the interface at an angle greater than the critical angle and is completely reflected back into the original medium. - Example: Light traveling from glass to air at a high angle totally reflects inside the glass. 3. **Refraction:** This is the bending of waves as they pass from one medium to another due to a change in speed. - Example: Light passing from air into glass bends towards the normal. 4. **Reflection:** This happens when a wave bounces back from the boundary between two media. - Example: Light hitting aluminium surface reflects back into the air. 5. **Two properties all waves share:** 1. They transfer energy from one place to another without the permanent transfer of matter. 2. Waves have characteristic properties such as wavelength, frequency, amplitude, and speed. --- 6. **Wi-Fi Signals Questions:** (a)(i) Both Wi-Fi signals at 2.4 GHz and 5.2 GHz are electromagnetic waves and can travel through air. (ii) The two signals have different frequencies and thus different wavelengths. (b)(i) The formula linking speed $v$, frequency $f$, and wavelength $\lambda$ is: $$v = f \times \lambda$$ (ii) Calculate wavelength of 5.2 × 10^9 Hz Wi-Fi signal: Given $v = 3.0 \times 10^{8}$ m/s and $f = 5.2 \times 10^{9}$ Hz, $$\lambda = \frac{v}{f} = \frac{3.0 \times 10^{8}}{5.2 \times 10^{9}} = 5.77 \times 10^{-2} \text{ meters}$$ (c)(i) Wi-Fi is an electromagnetic wave which is a transverse wave; therefore, the correct option is D (transverse). (ii) Difference between transverse and longitudinal waves: - In transverse waves, oscillations are perpendicular to the direction of wave travel. - In longitudinal waves, oscillations are parallel to the direction of wave travel. --- **Final answer summary:** - Total internal reflection, refraction, and reflection involve wave behavior at boundaries. - Two common wave properties: energy transfer and characteristic parameters. - Wi-Fi waves are electromagnetic, differ in frequency and wavelength. - Wavelength for 5.2 GHz Wi-Fi is approximately $5.77 \times 10^{-2}$ meters. - Wi-Fi signals are transverse waves.