Waves, sound and optics

A wave has a frequency of 50 Hz and a wavelength of 4 m. What is its speed?

• 1 12.5 m/s
• 2 54 m/s
• 3 200 m/s
• 4 400 m/s

Sound cannot travel through:

• 1 Water
• 2 Steel
• 3 Air
• 4 A vacuum

Light travels at 3 x 10^8 m/s in vacuum and 2 x 10^8 m/s in glass. What is the refractive index of the glass?

• 1 0.67
• 2 1.5
• 3 2.0
• 4 5.0

Total internal reflection occurs when light goes from:

• 1 A rarer to a denser medium at any angle
• 2 A denser to a rarer medium at an angle greater than the critical angle
• 3 A denser to a rarer medium at an angle less than the critical angle
• 4 Air into water at 90 degrees

What is the power of a lens whose focal length is 0.5 m?

• 1 0.5 D
• 2 1 D
• 3 2 D
• 4 5 D

When a wave passes from one medium to another, which quantity stays the same?

• 1 Speed
• 2 Wavelength
• 3 Frequency
• 4 Amplitude

A convex lens can form a real image when the object is placed:

• 1 Closer than the focal length
• 2 Beyond the focal length
• 3 At the lens itself
• 4 Only at infinity

As a source of sound moves towards a stationary listener, the listener hears:

• 1 A lower frequency
• 2 A higher frequency
• 3 No change in frequency
• 4 A lower speed of sound