This question is about waves in the electromagnetic (e.m.) spectrum - Edexcel - GCSE Physics Combined Science - Question 6 - 2022 - Paper 1

To calculate the wavelength $\lambda = \frac{v}{f}$

where:

• $v$ is the velocity of light ($3.00 \times 10^8$ m/s)
• $f$ is the frequency ($2.45 \times 10^9$ Hz)

Substituting in the values: $\lambda = \frac{3.00 \times 10^8 \text{ m/s}}{2.45 \times 10^9 \text{ Hz}}$

Calculating: $\lambda \approx 0.122 \text{ m}$ Therefore, the wavelength of the microwaves is approximately 0.122 m.

Given that the microwave oven is 55% efficient and transfers 42,000 J of energy:

Let $E_{supplied}$ be the total energy supplied to the device. The relationship is: $0.55 = \frac{42,000 J}{E_{supplied}}$

Rearranging gives: $E_{supplied} = \frac{42,000 J}{0.55} \approx 76,364 J$ Thus, the total amount of energy that must be supplied to the oven is approximately 76,364 J.

X-rays and radio waves are part of the electromagnetic spectrum, differing in frequency, wavelength, and uses.

Uses of X-rays:

• Medical diagnostics (e.g., detection of broken bones)
• Radiotherapy for cancer treatment
• Airport security screenings

Uses of Radio Waves:

• Broadcasting television and radio
• Enabling wireless communication (e.g., mobile phones)

Electron Involvement:

• X-rays are emitted when electrons transition between energy levels within an atom, emitting high-energy radiation.
• Radio waves, on the other hand, are generated by alternating current in circuits, where electrons oscillate, producing low-frequency signals.