SCIENCE 10 EM SPECTRUM - LESSON 11.pptx

SCIENCE 10 EM SPECTRUM - LESSON 11.pptx

1. ELECTROMAGNETIC WAVES LESSON 11

2. L ook around and think of: The light bulb in the classroom Their cellphone or radio The sunlight outside

3. How does light from the sun reach the Earth even without air in space? 2. How can your cellphone or radio work without wires?

4. Production of EM Waves Electromagnetic waves are produced when charged particles (like electrons) change speed or direction . Vibrating or moving electrons create changing electric and magnetic fields These fields continually regenerate each other: a changing electric field produces a magnetic field, and a changing magnetic field produces an electric fields.

5. Nature of EM Waves The electric and magnetic fields are oriented at right angles to each other and to the direction of wave motion. Because of this, electromagnetic waves are classified as transverse waves . Unlike mechanical waves, EM waves do not transfer energy by moving matter . Instead, the energy is carried by the oscillations of electric and magnetic fields.

6. Travel of EM Waves EM waves can travel through both a medium (such as air, glass, or water) and through a vacuum (empty space) . In a vacuum, they move at the speed of light, c = 3 × 10⁸ m/s . Their speed becomes slightly slower when passing through materials. Example: Light from the Sun travels about 150 million kilometers to reach Earth in roughly 8 minutes .

7. Speed, Frequency, and Wavelength All EM waves travel at the same speed in a vacuum , but they differ in wavelength and frequency . Frequency and wavelength are inversely proportional : as frequency increases, wavelength decreases. The amount of energy carried depends on frequency : higher frequency waves have greater energy.

8. Electromagnetic Spectrum The electromagnetic spectrum arranges EM waves by increasing frequency (or decreasing wavelength): Radio waves – longest wavelength, lowest frequency, lowest energy Microwaves Infrared Visible light Ultraviolet X-rays Gamma rays – shortest wavelength, highest frequency, highest energy

9. Energy of EM Waves EM waves carry energy in packets called photons . Low-frequency waves (radio, microwaves) have photons with low energy. High-frequency waves (X-rays, gamma rays, high ultraviolet) have photons with very high energy. Gamma rays, X-rays, and high UV are ionizing radiation , meaning their photons can remove electrons from atoms, causing ionization and chemical reactions .

10. where v is the wave speed, expressed in meters per second, the frequency f is expressed in Hertz and the wavelength λ is expressed in meters.

11. A wave has a frequency (f) = 5 Hz and a wavelength ( λ) = 2 m . What is the speed (v) of the wave? Solution: Formula: Substitute values: The wave speed is 10 m/s . ✅  

12. Problem 1 (Solve for Frequency): A sound wave travels at a speed of 340 m/s and has a wavelength of 0.85 m . What is the frequency ? f= v ​ / λ  

13. Problem 2 (Solve for Wavelength): A wave has a speed of 300 m/s and a frequency of 60 Hz . What is the wavelength ? Solution:  

14. Solve the following: 1. A wave has a frequency of 10 Hz and a wavelength of 3 m . What is its speed? 2. A wave travels with a speed of 300 m/s and has a frequency of 60 Hz . What is its wavelength? 3. An electromagnetic wave has a wavelength of 2 m and travels at the speed of light . What is its frequency? 4. A sound wave has a speed of 340 m/s and a wavelength of 0.85 m . Find its frequency. 5. An ocean wave has a frequency of 0.5 Hz and a wavelength of 4 m . What is its speed?