EmSAT EmSAT Physics 4 — Questions and Answers
Question 1: What is the speed of light in a vacuum?
- 3 × 10⁶ m/s
- 3 × 10⁸ m/s (Correct answer)
- 3 × 10¹⁰ m/s
- 3 × 10⁴ m/s
Correct answer: 3 × 10⁸ m/s
The speed of light in a vacuum is approximately 3 × 10⁸ m/s (300,000 km/s). This is a fundamental constant of nature denoted by c.
Question 2: What type of wave is sound?
- Transverse wave
- Electromagnetic wave
- Longitudinal wave (Correct answer)
- Surface wave
Correct answer: Longitudinal wave
Sound is a longitudinal (mechanical) wave where particles vibrate parallel to the direction of wave propagation. It requires a medium (solid, liquid, or gas) to travel.
Question 3: What happens to the frequency of a wave when its wavelength decreases (speed constant)?
- Frequency decreases
- Frequency stays the same
- Frequency increases (Correct answer)
- Frequency doubles then halves
Correct answer: Frequency increases
Wave speed = frequency × wavelength (v = fλ). If speed is constant and wavelength decreases, frequency must increase to maintain the equation.
Question 4: What is the Doppler effect?
- Light bending around obstacles
- Change in observed frequency due to relative motion (Correct answer)
- Wave reflection from a surface
- Wave energy decreasing with distance
Correct answer: Change in observed frequency due to relative motion
The Doppler effect is the change in observed frequency of a wave due to the relative motion between the source and the observer. A siren sounds higher as it approaches and lower as it moves away.
Question 5: Which type of electromagnetic wave has the highest frequency?
- Radio waves
- Visible light
- X-rays
- Gamma rays (Correct answer)
Correct answer: Gamma rays
Gamma rays have the highest frequency (and shortest wavelength) in the electromagnetic spectrum. They are produced by nuclear reactions and have the most energy.
Question 6: What is the law of reflection?
- The angle of incidence equals the angle of refraction
- The angle of incidence equals the angle of reflection (Correct answer)
- Reflected waves change speed
- Light bends toward the normal when entering a denser medium
Correct answer: The angle of incidence equals the angle of reflection
The law of reflection states that the angle of incidence equals the angle of reflection, both measured from the normal to the reflecting surface.
EmSAT EmSAT Physics 4
What is the speed of light in a vacuum?