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Light travels as a wave of electromagnetic radiation - Leaving Cert Physics - Question 9 - 2020
Question 9
Light travels as a wave of electromagnetic radiation. The colour of the light depends on its frequency. (i) Light is an example of a transverse wave. Explain what i... show full transcript
Worked Solution & Example Answer:Light travels as a wave of electromagnetic radiation - Leaving Cert Physics - Question 9 - 2020
Step 1
Explain what is meant by a transverse wave.
Answer
A transverse wave is characterized by oscillations that are perpendicular to the direction of wave propagation. In this type of wave, the disturbance moves in a direction that is at right angles to the wave's energy transfer. A common example is light waves, where the electric and magnetic fields oscillate perpendicular to each other and to the direction of the wave.
Step 2
Step 3
Describe an experiment to show that sound needs a medium to travel through.
Answer
An experiment can be conducted using a bell jar and a vacuum pump. Start with the bell jar containing a ringing electric bell. First, allow the sound to be heard in air. Then, use the vacuum pump to remove the air from the bell jar. As the air is evacuated, the sound will fade until it becomes inaudible. This demonstrates that sound requires a medium (in this case, air) to travel through.
Step 4
What is meant by reflection?
Answer
Reflection refers to the bouncing back of waves when they encounter a surface or an obstacle that does not absorb all the energy of the wave. This phenomenon is commonly observed with sound waves and light waves, leading to echoes and the perception of images, respectively.
Step 5
Describe an experiment to show the interference of sound waves.
Answer
To observe the interference of sound waves, one can use two tuning forks of the same frequency. Strike both forks simultaneously and place them at a distance from the ear. As the sound waves propagate, they will overlap and create regions of constructive and destructive interference, resulting in variations in loudness. This can be demonstrated by moving to different positions to experience the differences in sound intensity.
Step 6
Sound waves do not undergo polarisation. Explain why.
Answer
Sound waves are longitudinal waves, meaning the oscillations occur in the same direction as the wave travels. This characteristic makes it impossible for sound waves to be polarized, as polarization requires a transverse wave, where oscillations can be restricted to a particular plane.
Step 7
Describe a laboratory experiment to demonstrate the Doppler effect.
Answer
A simple experiment to demonstrate the Doppler effect involves using a moving sound source, such as a buzzer, and a stationary observer. As the buzzer approaches the observer, the sound frequency increases, leading to a higher pitch. Conversely, as it moves away, the frequency decreases, resulting in a lower pitch. This effect can be portrayed by moving the sound-emitting device along a straight path past the observer.
Step 8