What type of wave is light?

A longitudinal mechanical wave, like sound An electromagnetic wave — oscillating electric and magnetic fields perpendicular to each other and to the direction of travel A stream of tiny material particles with no wave properties A pressure wave that requires air or another medium to travel

What is the speed of light in a vacuum?

340 m/s 3 × 10⁶ m/s Approximately 3 × 10⁸ m/s (299,792,458 m/s) Infinite — light travels instantaneously

Does light need a medium to travel through?

Yes — light requires a special medium called the aether Yes — light needs air to vibrate, like sound No — light is an electromagnetic wave and can travel through a vacuum Only in space — on Earth, light requires air

Light from the Sun takes approximately 8 minutes to reach Earth. What does this tell us?

Light is slow — it takes 8 minutes to travel even a short distance The Sun's light is much weaker than artificial light, so it takes longer to arrive The Sun is approximately 150 million km away (8 min × 300,000 km/s = 144,000,000 km ≈ 1.5 × 10⁸ km) Light travels more slowly through space than through air

What are the wavelengths of visible light?

1 mm to 1 m Approximately 380 nm (violet) to 700 nm (red) 0.1 nm to 1 nm 1 m to 1 km

When light passes from a vacuum into glass, its speed decreases to about 2 × 10⁸ m/s. Does the frequency change?

Yes — the frequency doubles as the wave enters the denser medium No — the frequency stays the same; only the wavelength shortens in proportion to the speed Both frequency and wavelength increase inside glass The frequency decreases by the same factor as the speed

James Clerk Maxwell predicted the existence of electromagnetic waves in 1865. How did he derive this prediction?

He measured the speed of light directly with mirrors and a spinning wheel He observed that electric fields bend light, proving they are related From his four equations of electromagnetism, he showed that oscillating electric and magnetic fields could propagate as waves at a speed matching the known speed of light He found that magnets slow down light, suggesting they are connected

When you look at a star 100 light-years away, what are you actually seeing?

The star as it is right now — modern telescopes show real-time images The star as it was 100 years ago — the light you are receiving left the star 100 years in the past A reflection of the star from nearby space dust The star as it was billions of years ago — space expands and slows light

Why is the speed of light in vacuum considered a fundamental constant of nature?

It is the fastest possible speed, so it is used as a reference All observers measure the same value for c regardless of their motion or the motion of the source — this universality is built into the structure of spacetime It was the first speed ever measured, so it was defined as the universal constant The speed of light is constant only in vacuum — in any medium it varies

Which of the following correctly describes polarisation of light?

Polarisation is the splitting of light into its component colours by a prism Polarisation restricts the oscillation of the electric field of light to a single plane — only transverse waves can be polarised Polarisation occurs when light passes through a vacuum and gains extra energy Polarisation is the slowing of light as it enters a denser medium