Electromagnetic Waves Quiz

Electromagnetic Waves and Properties of Light

• Electromagnetic waves (EM waves) are created by disturbances in electromagnetic fields, such as light.
• All matter emits EM waves due to moving charged particles.
• Wavelengths shorten as material temperature increases.
• EM waves carry radiant energy.
• Light is a transverse wave with varying electric and magnetic fields.
• EM waves travel at 300,000 km/s in a vacuum (speed of light).
• Speed of EM waves decreases in denser materials (e.g., solids > gases).
• Light travels in straight lines.
• Light reflects off polished surfaces.
• Light refracts when entering different media.
• Light propagates in a vacuum and matter.

Periodic Motion Examples

• Disturbing water surface creates water waves.
• Sound waves are created by disturbing air molecules.
• Light waves are generated by disturbances in electromagnetic fields.

Properties of EM Waves

• All matter contains moving charged particles and consequently emits EM waves.
• Shorter wavelengths correspond to higher temperatures.
• EM waves carry radiant energy.
• Light is a transverse wave of varying electric and magnetic fields.
• The oscillating fields propagate through space.

Speed of EM Waves

• All EM waves travel at 300,000 km/s in a vacuum (speed of light).
• Speed differs slightly in various materials:
  • Vacuum: 300,000 km/s
  • Air: less than 300,000 km/s
  • Water: 226,000 km/s
  • Glass: 200,000 km/s
  • Diamond: 124,000 km/s

General Properties of Light

• Light travels in straight lines.
• Light reflects off polished surfaces.
• Light refracts at the boundary between two different media.
• Light propagates in both vacuum and matter.
• Light's speed in a vacuum is 3 x 10⁸ m/s.
• Speed in medium (v) = speed in vacuum (c) / refractive index of medium (n)

Wavelength and Frequency of EM Waves

• Wavelength: distance between two successive crests.
• Frequency: number of wavelengths that pass a specific point in one second.
• Frequency increases, wavelength decreases.
• Different wavelengths interact with matter uniquely.
• Visible light constitutes a small portion of the EM spectrum.

The Electromagnetic Spectrum

• The EM spectrum encompasses a range of electromagnetic waves with varying wavelengths and frequencies.
• The full EM spectrum can be divided into various regions with different characteristics.
• Radio waves: lowest frequency, longest wavelength
• Microwaves: used for communication and cooking.
• Infrared: heat radiation.
• Visible light: perceived by the human eye.
• Ultraviolet: used for sterilization, vitamin D production.
• X-rays: used for medical imaging.
• Gamma rays: highest frequency, shortest wavelength, high energy, most harmful.

Devices Detecting Other Frequencies

• Radio waves are detected by antennae, and converted into sound waves.
• Microwaves are used in cell phones and satellites for communication.

What are Microwaves?

• Microwaves are radio waves with wavelengths less than 30 cm and higher frequency.
• Cell phones and satellites use microwaves for communication.
• Microwave ovens use microwaves to heat food by causing water molecules to rotate rapidly and create friction which generates heat.

Magnetic Resonance Imaging (MRI)

• MRI uses radio waves to diagnose illnesses, along with a strong magnet and radio wave emitter/receiver.
• Protons in the body's hydrogen atoms act like tiny magnets, aligning with the external magnetic field.
• When the magnetic field is altered, the protons release energy, which the receiver detects, creating a map of body tissues.

Infrared Waves

• EM waves with wavelengths between 1 mm to 700 nm
• Used in remote controls, CD players to read CD-ROMs.
• Every object emits infrared waves proportional to its temperature (hotter emit more)
• Used in satellite surveillance to identify plant types in a region.
• Divided into Near, Medium, and Far Infrared regions.

Applications of Infrared Waves

• Heat Source (industrial use): uses infrared radiation as a heat source
• Medical Uses: infrared saunas to treat high blood pressure and rheumatoid arthritis, a safe physiotherapy method.
• Massage Therapy: uses infrared rays to warm the skin and relax muscles.
• Infrared rays penetrate the skin readily.

Visible Light

• Range of EM waves visible to humans.
• 700 nm (red light) to 30 nm (violet light).
• Blue light has the shortest wavelength.
• Red light has the longest wavelength.
• Light appears white if all colors are present.
• Visible light are a small part of the EM spectrum

Remembering the Order of Visible Light Colors

• ROY G BIV (Red, Orange, Yellow, Green, Blue, Indigo, Violet)

Ultraviolet Waves

• EM waves with wavelengths from 400 nm to 10 nm.
• UV light is emitted by the Sun
• Divided into UV A, UV B and UV C.
• UV-C: very harmful and largely absorbed in the atmosphere
• UV-B: causes sunburns and damages DNA of living organisms. about 95% of UV-B rays are absorbed by ozone in the atmosphere.
• UV rays that reach the earth's surface can cause sunburns, increase the risk of skin cancer and cataracts.

Can UV Radiation Be Useful?

• Helps the body produce vitamin D, important for healthy bones and teeth.
• Used to sterilize medical equipment.
• Detectives use UV fluorescence powder to find fingerprints.

Ionizing and Non-Ionizing Radiation

• Non-ionizing radiation includes Radio Frequencies, Visible Light and Infrared.
• Ionizing radiation includes X-rays and Gamma rays.
• High frequency radiation carries more energy than low frequency radiation.

Wavelength Regions in the Electromagnetic Spectrum

• The spectrum displays the range of wavelengths for electromagnetic waves, showing energy variation across each type of wave.

X-Rays and Gamma Rays

• X-rays and gamma rays are high energy radiation.
• X-rays are used for medical imaging (due to their ability to pass through tissues, but be absorbed by bones/metals).
• Gamma rays have shorter wavelengths & higher energy levels and are used for medical imaging and cancer treatment techniques
• High level exposure causes cancer.

MRI Uses

• Doctors use to get a detailed look at the brain (strokes, tumors, multiple sclerosis).
• MRI also examines nerves, muscles, ligaments, tendons, spinal cord, nerve roots, and ligaments, that support the spine.

X-Ray Uses

• X-rays detect fractures, foreign objects, tumors (especially in lungs), some pneumonia complications, dental cavities, calcification, heart failure, kidney stones, bowel obstructions, and arthritis.
• In cases of cancer, X-rays / radiation therapy is used to destroy DNA inside cancer cells.

Wavelengths in the Electromagnetic Spectrum

• Displays the spectrum in relation to wavelength and frequency.

Why are Ultraviolet, X-Rays, and Gamma Rays Dangerous?

• High energy forms of radiation.
• Are ionizing radiation which is capable of breaking chemical bonds in cells, damaging DNA.
• Repeated or high dose exposure can lead to health problems (such as cancers).
• Body can usually repair some cellular damage but too much damage will cause cancer.

Lenses and Mirrors

• Light, lenses and mirrors can be used to refract, reflect or change the direction and form of light to produce images.

Refraction of Light

• Light passing from one medium to another changes speed and can bend.
• Refraction is affected by the refractive indices of the two media.
• Refractive indices measure the relative ease with which light travels through different materials.
• Light traveling from a less optically dense medium to a more optically dense medium bends towards the normal.
• Light traveling from a more optically dense medium to a less optically dense medium bends away from the normal.

Snell's Law of Refraction

• The ratio of the sine of the angle of incidence to the sine of the angle of refraction is equal to the ratio of the refractive indices of the two media.

Quick Quizzes - Examples

• Includes various practical examples demonstrating the application of equations and principles.

Critical Angle

• The critical angle is the incident angle that produces a 90^o angle of refraction.
• Total internal reflection occurs only when light travels from a medium with a (relatively) higher optical density to a lower one, and the angle of incidence exceeds the critical angle.

Fiber Optics

• Uses extremely thin strands of glass or transparent fibers to transmit light and information over long distances.
• Fiber optic signals are invulnerable to electrical interference, ensuring distortion-free transmission.
• Flexible material allowing information to travel with ease in communication and information transfer systems.
• Individual fibers in cable bundles, can have diameters ranging from 0.002 mm to 0.01 mm.

Fiber Optics Applications

• Diverse applications in medical examination (endoscopes), communication systems, and modulated laser beams.
• Light (radio) waves are proportional to the frequency for information transfer.

Lens-Maker Equation

• The equation that determines the focal length of a lens in relation to the refractive index of the lens material and the radii of curvature of both lens surfaces.
• A positive radius signifies the curvature is on the opposite side of the incident light's path.
• A negative radius signifies the curvature is in the same direction as the path of the incident light.

Homework (H. W) Problems

• Includes practical lens and spherical mirror problems that are solved according to mathematical and optical physics principles and laws.

X-Rays and Gamma Rays - Safety

• X-rays and Gamma rays may be dangerous, but extensive studies have not consistently linked their use to significant health issues.
• Studies have found no notable increase in cancer for workers exposed to X-rays and gamma rays

Summary of Eye Parts (Structure and Functionalities)

• Describes the structure and function of the various eye parts: (cornea, aqueous humor, lens, vitreous humor, iris, pupil, ciliary muscles, retina and optic nerve).

Accommodation of Eye

• Accommodation is the process of the eye changing its optical power to adjust focus to a specific distance.
• The eye maintains focus using the adjustable crystalline lens
• The ciliary muscles alter lens curvature to adjust focus on objects at varying distances..
• Accommodation allows the eye to focus on nearby or distant objects.

The Far and Near Points of the Eye

• The far point is the furthest distance an object can be from the eye and still be in sharp focus.
• The far point of normal vision is at infinity
• The near point is the closest distance an object can be from the eye and still be in sharp focus.
• The near point is approximately 25 cm for normal vision but it decreases with age.

Sight Defects

• Common eye defects include Myopia (Near-sightedness), Hypermetropia (Far-sightedness), Presbyopia (Loss of Accommodation due to eye aging), and Astigmatism.
• Each defect is described, cause, and how each can be corrected (using different types of spectacle/corrective lenses)

Astigmatism

• Astigmatism is an eye defect where the eye's focusing power differs in various directions due to an asymmetry in the lens's curvatures or the eye's refracting surfaces.
• It can be corrected using asymmetric lenses astigmatic lenses designed to compensate for the asymmetric focusing power differences.

Prescription of Eye Test

• How to interpret the results of eye tests relating to eye health, defects (or issues) and corrective measures (i.e. eyeglasses or contact lenses prescriptions)

Lens Maker Equation

• Formula used to calculate a lens's focal length, given its material's refractive index and the radii of curvature of its surfaces.
• Provides a methodology for determining focal length in a variety of corrective lens contexts

Homework (H.W) Problems - Lens Problems

• A collection of problems to calculate lens focal length and refractive index which are solved using the mathematical principles of optics

Electromagnetic Wave Summary

• Summary of the different types of Electromagnetic waves, their characteristics, and uses

Test your knowledge on electromagnetic waves with this quiz. Explore topics such as their creation, behavior with temperature changes, speed in a vacuum, and classification of light. Perfect for physics enthusiasts and students!