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Electromagnetic Waves and the Invisible Spectrum

Worksheet
Grade 9
English

Electromagnetic Waves and the Invisible Spectrum

Introduction to Electromagnetic Radiation

Electromagnetic (EM) waves are a synchronized dance of electric and magnetic fields that travel at the ultimate speed limit of the universe. Unlike mechanical waves, they do not require a medium (like air or water) and can travel through the pure vacuum of space.
fig 1: Educational illustration of a glass prism dispersing a beam of white light into the full visible spectrum (ROYGBIV) to demonstrate the interaction of dispersion.
fig 1: Educational illustration of a glass prism dispersing a beam of white light into the full visible spectrum (ROYGBIV) to demonstrate the interaction of dispersion.



Activity 1: The Blueprint of a Wave

Difficulty: Easy/Moderate
Identify the key parts of the transverse wave diagram below. Use the terms provided in the word bank and write the correct label next to each number.
Word Bank (Shuffled):
  • Wavelength
  • Trough
  • Crest
  • Equilibrium Line
  • Amplitude
fig 2: Transverse Wave Diagram
fig 2: Transverse Wave Diagram

  1. 
  1. 
  1. 
  1. 
  1. 


Activity 2: The Medical Spectrum (Matching)

Difficulty: Moderate
Electromagnetic radiation is used extensively in modern medicine. Match the Wave Type on the left with its corresponding Medical Modality or Treatment Mechanism on the right by writing the correct letter in the space provided.
Wave Type
Answer
Medical Modality / Mechanism
1. Radio Waves
____
A. Endoscopy cameras for internal surgery.
2. Microwaves
____
B. Structural radiography for dental imaging.
3. Infrared
____
C. MRI (Magnetic Resonance Imaging) for soft tissue.
4. Visible Light
____
D. Gamma Knife for highly focused brain tumor treatment.
5. Ultraviolet
____
E. Diathermy for targeted deep tissue pain management.
6. X-Rays
____
F. Phototherapy for treating Psoriasis and Vitiligo.
7. Gamma Rays
____
G. Thermography for vascular and respiratory mapping.


Activity 3: Properties of EM Radiation

Difficulty: Easy
Select the best answer for each question regarding the nature of electromagnetic waves.
  1. Which of the following is NOT a property of all electromagnetic waves? A. They require a gas or liquid medium to travel. B. They consist of oscillating electric and magnetic fields. C. They travel at the speed of light in a vacuum. D. They are transverse waves.
  1. How are wavelength and frequency related in the electromagnetic spectrum? A. They are inversely proportional (as wavelength increases, frequency decreases). B. They are not mathematically related. C. They are directly proportional (both increase together). D. They both remain constant regardless of wave type.


Activity 4: Calculating Wave Properties

Difficulty: Difficult
Use the wave speed formula to solve the following problems. Show your work clearly.
Constant: Speed of light

Formula:

(where

is wavelength and

is frequency)
  1. A local radio station broadcasts at a wavelength of
    
    . Calculate the frequency of the radio waves emitted by the station.
Calculation:
Answer: ________________________________
  1. A specific shade of green light has a frequency of
    
    . What is its wavelength in meters?
Calculation:
Answer: ________________________________


Activity 5: Crossing the Ionizing Boundary

Difficulty: Moderate
Fill in the gaps to complete the explanation of radiation hazards based on the concept of ionization.
Electromagnetic waves are divided into two categories based on their energy levels: non-ionizing and ionizing.
Waves such as Radio, Microwave, Infrared, and __________________ are non-ionizing. These waves lack the energy to remove __________________ from atoms. Their primary physiological effect is usually __________________ (like the warmth felt from a fire).
However, once the spectrum passes the Violet light threshold, waves become energetic enough to be ionizing. These include __________________, X-Rays, and Gamma Rays. These high-energy waves can successfully knock electrons out of atoms, which can directly sever __________________ structures, leading to cellular mutation and increased cancer risk.