PRELIMINARY STAGE 2024
Contest 7
Tepa SHS: 40 points (Winner)
Bright SHS: 39 points
Sekondi College: 27 points
Contest 8
Queen of Peace SHS: 34 points (Winner)
Sonrise Christian High School: 31 points
Presby SHS, Bompata: 30 points
Contest 9
Navrongo SHS: 39 points (Winner)
St. Mary’s Seminary SHS, Lolobi: 36 points
Bolgatanga Girls’ SHS: 29 points
ROUND 5 - RIDDLE
RIDDLE
I am a type of wave.
I can be traveling or standing.
I can be diffracted but not polarized.
I can be diffracted but not polarized.
My name recalls a cartographic coordinate.
I am the type of wave in which particle oscillations occur parallel to the direction of wave.
WHO AM I?
ANSWER: LONGITUDINAL WAVE
EXPLANATION:
In a longitudinal wave the particles oscillate parallel to the direction the wave travels, as in sound.
It can be diffracted but not polarised, and its name recalls longitude.
NOTE: The clue "I can be diffracted but not polarized." appears twice in the original riddle.
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PRACTICE QUESTIONS
1. RIDDLE:
I am a type of wave.
I can be travelling or standing.
I can be polarised.
My particles oscillate at right angles to my direction of travel.
Waves on a stretched string are examples of me.
Light is an example of me.
Who am I?
ANSWER: TRANSVERSE WAVE
EXPLANATION:
In a transverse wave the oscillations are perpendicular to the direction of travel.
2. RIDDLE:
I am a type of wave.
I need a material medium to travel through.
I cannot cross a vacuum.
My energy passes from particle to particle.
Sound and water waves are examples of me.
Earthquake waves are examples of me too.
Who am I?
ANSWER: MECHANICAL WAVE
EXPLANATION:
A mechanical wave needs a medium; sound cannot travel through a vacuum.
3. RIDDLE:
I am a type of wave.
I need no medium.
I travel at about three hundred million metres per second in a vacuum.
I am made of oscillating electric and magnetic fields.
Radio waves, light and X-rays are all examples of me.
Maxwell predicted me.
Who am I?
ANSWER: ELECTROMAGNETIC WAVE
EXPLANATION:
Electromagnetic waves are transverse oscillations of electric and magnetic fields that travel through a vacuum at c.
4. RIDDLE:
I am a type of wave.
Two identical waves travelling in opposite directions form me.
I do not transfer energy along my length.
I have points that never move.
I have points of maximum vibration between them.
A plucked guitar string vibrates as me.
Who am I?
ANSWER: STANDING WAVE
EXPLANATION:
A standing (stationary) wave has fixed nodes and antinodes and no net energy transfer.
5. RIDDLE:
I am a type of wave.
I carry energy from one place to another.
My crests move forward.
Every particle along me has the same amplitude.
Neighbouring particles along me are out of phase.
I am also called a travelling wave.
Who am I?
ANSWER: PROGRESSIVE WAVE
EXPLANATION:
A progressive wave transfers energy; its profile moves along the medium.
6. RIDDLE:
I am a type of wave.
I am mechanical and longitudinal.
I travel faster in solids than in air.
I cannot pass through a vacuum.
My frequency decides my pitch.
Your ears detect me.
Who am I?
ANSWER: SOUND WAVE
EXPLANATION:
Sound is a longitudinal mechanical wave of compressions and rarefactions.
7. RIDDLE:
I am a type of wave.
I travel through the Earth.
An earthquake produces me.
My primary kind is longitudinal and arrives first.
My secondary kind is transverse and cannot cross liquids.
Seismometers record me.
Who am I?
ANSWER: SEISMIC WAVE
EXPLANATION:
Seismic P-waves are longitudinal; S-waves are transverse and cannot travel through liquids.
8. RIDDLE:
I am a type of wave.
I travel along the boundary between two media.
Ripples on a pond are an example of me.
My particles move in circles or ellipses.
I lose strength with depth below the surface.
Surfers ride on me at the beach.
Who am I?
ANSWER: WATER WAVE
EXPLANATION:
Water surface waves combine transverse and longitudinal motion, so particles move in circular paths.
9. RIDDLE:
I am a type of wave.
I am a sudden, very strong pressure disturbance.
A source moving faster than sound creates me.
I cause a sonic boom.
An explosion also produces me.
My front is cone-shaped behind a supersonic aircraft.
Who am I?
ANSWER: SHOCK WAVE
EXPLANATION:
A shock wave forms when a source moves faster than the wave speed in the medium.
10. RIDDLE:
I am a type of wave.
My wavefronts are flat and parallel.
Far from a point source, spherical waves look like me.
My rays are all parallel.
A collimated beam of light is an example of me.
My name comes from the flat surface in geometry.
Who am I?
ANSWER: PLANE WAVE
EXPLANATION:
A plane wave has flat, parallel wavefronts and parallel rays.
11. RIDDLE:
I am an electromagnetic wave.
I have the longest wavelengths in the spectrum.
Antennas send and receive me.
I carry broadcasts over long distances.
I can be reflected by the ionosphere.
AM and FM stations use me.
Who am I?
ANSWER: RADIO WAVE
EXPLANATION:
Radio waves have the longest wavelengths and are used for broadcasting and communication.
12. RIDDLE:
I am an electromagnetic wave.
My wavelength is between that of radio waves and infrared.
Radar uses me.
Mobile phones and Wi-Fi use me.
I make water molecules in food vibrate.
An oven that heats food quickly is named after me.
Who am I?
ANSWER: MICROWAVE
EXPLANATION:
Microwaves have wavelengths from about a millimetre to about thirty centimetres; they heat water molecules.