Wave Properties
What is the formula for wave speed?
Wave speed formula: v=distancetimev=timedistance
What is reflection?
Reflection: wave bounces back from a boundary.
Which medium does sound travel fastest in: solids, liquids, or gases?
Sound travels fastest in solids.
Do electromagnetic waves all travel at the same speed in a vacuum? (Yes or No)
Yes — electromagnetic waves all travel at the same speed in a vacuum (the speed of light).
Scientists use evidence to support their ideas. Give one example of evidence scientists might collect in an experiment about shadows.
Example evidence: measurements of shadow length at different times, or photos showing shadow position.
What is the name for the distance between two corresponding points on adjacent waves (like crest to crest)?
Wavelength: λλ, the distance between corresponding points on adjacent waves (crest to crest or trough to trough).
What is refraction?
Refraction: wave changes direction when passing between media with different speeds.
Which of these is a transverse wave: sound in air, light waves, seismic P waves, or sound in water?
Light waves (are transverse).
Name one property that electromagnetic waves can differ in (frequency or wavelength).
They can differ in frequency or wavelength.
Why do scientists use different tools when investigating? Give one specific example of a tool and what it measures.
Different tools give different measurements: e.g., a ruler measures shadow length; a stopwatch measures time.
What is diffraction? Give a one-sentence definition.
Amplitude: maximum displacement from rest position.
What is diffraction?
Diffraction: wave bends around obstacles or through openings.
Sea water contains salt. Name one property of a wave that could change because of salt in the water (speed, wavelength, frequency, or type) and briefly explain why.
Salt can change wave speed (true) because adding salt changes the density and properties of the water, which affects how quickly waves travel; wavelength may change while frequency stays the same for wave crossing media.
Explain briefly why light can cast a shadow.
Light travels in straight lines; when an object blocks light, it prevents light from reaching some area, producing a shadow.
Draw a simple diagram (on paper) that shows how an object makes a shadow when the Sun is overhead. Label the light source, object, and shadow. (Teacher: ask students to sketch — no answer provided here.)
Sketch
If a wave has frequency 2 Hz and wavelength 3 m, what is its speed?
Calculation: frequency f=2 Hzf=2 Hz, wavelength λ=3 mλ=3 m, speed v=fλv=fλ so v=2×3=6 m/sv=2×3=6 m/s.
What is interference? Describe constructive and destructive interference in one sentence each.
Interference: when two or more waves meet; constructive interference = amplitudes add (reinforce), destructive interference = amplitudes subtract (cancel).
Which statement best describes how wind affects the surface of the sea: slower wind makes the sea ___; faster wind makes the sea ___? (Fill in blanks.)
Slower wind → sea is smoother; faster wind → sea is rougher.
Which of these statements is true about electromagnetic waves in vacuum: (a) highest frequency, (b) biggest wavelength, (c) same speed in vacuum, (d) varying speed in vacuum? Choose the best answer and explain.
Best answer: (c) same speed in vacuum. Explanation: All electromagnetic waves travel at the constant speed of light in vacuum.
Explain why shadows change shape during the day in one or two sentences.
Shadows change shape because the Sun’s position (angle) changes during the day, which changes the angle of incoming light and the length/direction of the shadow.
Explain how frequency, wavelength, and wave speed are related. Write the formula and describe in one sentence how changing frequency affects wavelength when speed is constant.
Relationship: v=fλv=fλ. If speed vv is constant and frequency ff increases, then wavelength λλ must decrease.
A wave passes from air into water and bends toward the normal. Which interaction is this and why does it bend toward the normal?
This is refraction; the wave bends toward the normal because it slows down entering the denser medium (water) from a less dense medium (air).
Wax is more flexible than wood. Which of the following are likely true: (i) wax has a lower wave speed than wood, (ii) the wavelength in wax is different from wood, (iii) the frequency in wax is higher than in wood. For each, write True or False and give a one-sentence reason.
(i) Likely True — more flexible (less stiff) materials often have lower wave speeds. (ii) True — wavelength can differ because speed differs while frequency from the source remains the same. (iii) False — frequency is usually determined by the source and does not change when the wave moves into a different material.
Describe one difference between mechanical waves and electromagnetic waves (include at least one example).
Mechanical waves need a medium (e.g., sound needs air), electromagnetic waves do not (e.g., light travels through vacuum).
Design a short investigation: State a question about how the Sun’s position affects shadow length, list one variable to change, one variable to keep the same, and one measurement you will record.
Question — How does the Sun’s angle affect shadow length? Change — time of day (or Sun angle), Keep same — object height and surface, Measure — shadow length in centimeters every hour.