Question 1: Define the term 'colour' as it relates to light.

Answer: Colour is the perception of different wavelengths of light by the human eye.

Question 2: Explain how a white object appears coloured under white light.

Answer: A white object appears coloured because it reflects certain wavelengths of light while absorbing others.

Question 1: Calculate the wavelength of red light with a frequency of 4.3 × 10^14 Hz. (Speed of light, c = 3.0 × 10^8 m/s)

Answer: Wavelength λ = c / f = (3.0 × 10^8 m/s) / (4.3 × 10^14 Hz) ≈ 6.98 × 10^-7 m

Question 2: Determine the energy of a photon of blue light with a wavelength of 470 nm. (Planck's constant, h = 6.63 × 10^-34 Js)

Answer: Energy E = h × c / λ = (6.63 × 10^-34 Js) × (3.0 × 10^8 m/s) / (470 × 10^-9 m) ≈ 4.23 × 10^-19 J

Question 1: Describe a simple experiment to demonstrate that different wavelengths of light produce different colours. Mention the materials and safety precautions.

Answer: Use a diffraction grating or a prism to split white light into its component colours. Ensure safety by wearing safety goggles and handling the equipment carefully to prevent glare or injury.

Question 2: What variables must be controlled when measuring the wavelength of light using a diffraction grating?

Answer: The distance between the diffraction grating and the screen, the angle of diffraction, and the wavelength of the incident light should be controlled for accurate measurements.

Question 1: A material absorbs all wavelengths of visible light except for green, which it reflects. Explain what colour the material appears to the human eye and why.

Answer: The material appears green because it reflects green wavelengths and absorbs all others.

Question 2: In a fibre optic communication system, light of wavelength 1550 nm is used. Calculate its frequency. (Speed of light, c = 3.0 × 10^8 m/s)

Answer: Frequency f = c / λ = (3.0 × 10^8 m/s) / (1550 × 10^-9 m) ≈ 1.935 × 10^14 Hz

Question 1: Explain how understanding the properties of visible light is important in designing energy-efficient lighting systems.

Answer: Knowing the wavelengths and energy of different light sources allows engineers to select appropriate lighting that maximises efficiency and colour rendering, reducing energy consumption and improving visual comfort.

Question 2: A smartphone camera uses a filter that only allows green light to reach the sensor. Describe a practical reason for this choice.

Answer: Green filters improve image clarity and detail because human eyes are most sensitive to green light, enhancing colour accuracy and contrast.