Waves Basics — Set 3

Correct Answer: A. k = 2π/λ

k = 2π/λ is correct because wave number measures spatial angular variation. Its SI unit is per meter (m⁻¹). Larger k means shorter wavelength.

Correct Answer: C. ω = 2πf

ω = 2πf is correct because one cycle equals 2π radians. Angular frequency is measured in rad/s. It is widely used in wave and oscillation equations.

Correct Answer: D. 10 m/s

Option D is correct because v = fλ = 5 × 2 = 10 m/s. Wave speed equals frequency times wavelength. At fixed speed, higher frequency means smaller wavelength.

Correct Answer: A. 2 m

Option A is correct because λ = v/f = 340/170 = 2 m. Wavelength is the distance covered in one cycle. For a given speed, higher frequency gives smaller wavelength.

Correct Answer: C. Solids

Solids are correct because particles are closely packed and transmit vibrations quickly. Gases have larger particle spacing, so sound travels slower. Sound cannot travel through vacuum because there is no medium.

Correct Answer: A. Less than 20 Hz

Less than 20 Hz is correct because it lies below normal human hearing. Such low frequencies can travel long distances in air. Some animals can sense infrasonic sounds.

Correct Answer: C. per meter (m⁻¹)

The correct answer is 'per meter (m⁻¹)'. m⁻¹ is correct because wave number represents spatial frequency per unit length. It is often defined as 2π/λ in rad/m. Shorter wavelength means larger wave number.

Correct Answer: A. Speed in the new medium

Speed change is correct because waves travel at different speeds in different media. Frequency stays fixed by the source, so wavelength adjusts. Refraction causes bending when speed changes across a boundary.

Correct Answer: D. Amplitude of the wave

Amplitude is correct because speed mainly depends on medium properties in linear waves. For example, tension and mass per length set speed on a string. Very large amplitudes can cause nonlinear effects, but basic models assume small amplitudes.

Correct Answer: C. Louder sound

Louder sound is correct because amplitude relates to intensity of sound. Pitch depends mainly on frequency, not amplitude. Greater amplitude carries more energy through the medium.