<p align="right">Last Update: <font color="#4f81bd">July, 16, 2024</font></p> ## BIG IDEAS - **Electromagnetic waves** can be divided into three “categories.” - Visible light - Infrared, radar, radio (low energy) - Ultraviolet, x-ray, and gamma rays (high energy) ### Categories of [[Electromagnetic radiation]] Gamma ray - High energy and penetrating rays - Earth’s atmosphere absorbs any gamma ray that reaches the planet. - Can destroy living cells. - Used to kill cancer cells. X-ray - High energy rays - Can penetrate hard objects. - Use in imaging in hospitals and luggage screening. Ultraviolet - High energy - Can cause sunburn and skin cancer - The ozone layer absorbs most UV from our Sun. Visible light - Our eyes are sensitive to visible light. - Waves lead to our seeing. - Consists of seven colors of different wavelengths: ROYGBIV Infrared rays - Responsible for transferring heat energy. - The warmth of the Sun is infrared. - Useful in remote controls Microwave - Lower wavelength - Can penetrate objects and deposit heat. - Used in microwave ovens. - Used in satellite communications. Radio wave - Lowest wavelength in the electromagnetic spectrum. - Used in TV, radio, and cell phones. ### Determining the EM Spectrum - **1800 - Discovery of Infrared Radiation**: - **Scientist**: William Herschel - **Key Experiment**: Herschel passed sunlight through a prism to create a spectrum and used thermometers to measure temperature beyond the visible red light, discovering infrared radiation. - **1801 - Discovery of Ultraviolet Radiation**: - **Scientist**: Johann Wilhelm Ritter - **Key Experiment**: Ritter used silver chloride, which darkens when exposed to light, and found that the darkening effect was strongest just beyond the violet end of the visible spectrum, discovering ultraviolet radiation. - **1864 - Prediction of Electromagnetic Waves**: - **Scientist**: James Clerk Maxwell - **Key Contribution**: Maxwell formulated the equations of electromagnetism, predicting the existence of electromagnetic waves and suggesting that light was a form of electromagnetic radiation. - **1887 - Discovery of Radio Waves**: - **Scientist**: Heinrich Hertz - **Key Experiment**: Hertz generated and detected radio waves in the laboratory, providing experimental confirmation of Maxwell's theory by demonstrating that these waves exhibited similar properties to light, such as reflection and refraction. - **1895 - Discovery of X-rays**: - **Scientist**: Wilhelm Conrad Roentgen - **Key Experiment**: Roentgen discovered X-rays while experimenting with cathode rays, observing that they could pass through materials and produce images on photographic plates. --- Return [[Home|Home]] | [[Oscillations]] | [[Electromagnetic radiation]] | [[Speed of Light]] | [[Wave Equation]]