In a movie, while showing the explosion of a spacecraft in space, a flash of light. Class 9

In a movie, while showing the explosion of a spacecraft in space, a flash of light. Class 9

Question 1.

In a movie, while showing the explosion of a spacecraft in space, a flash of light is shown along with sound at the same time. What are the errors in this depiction? Class 9

Answer:

There are two errors:

(i) Sound cannot travel in space (vacuum): Outer space has near vacuum - there is no medium for sound to propagate. Sound is a mechanical wave and requires a material medium. So, no sound from the explosion should be heard.

(ii) Light and sound travel at vastly different speeds: Even if sound could somehow travel in space, light travels much faster (300,000 km s^-1) than sound (approximately 340 m s^-1 in air). So they would not be perceived simultaneously from any significant distance. The flash of light would be seen far before any sound (if it could exist) would be heard.

Question 2.

A source produces a sound wave of wavelength 3.44 m. If the wave travels with a speed of 344 m s^-1 find its time period. Class 9

Answer:

Using v = λ × v: v = v/λ = 344 / 3.44 = 100 Hz

Time period T = 1/v = 1/100 = 0.01 s