Waves Study Sheet - NILE Egyptian International Schools - PDF

NILE Egyptian international schools Science department Physics WAVES study sheet 1  Subject Grade Date Block week Unit/Lesson/Topic sheet physics 9 8/9/2024 1...

NILE Egyptian international schools Science department Physics WAVES study sheet 1  Subject Grade Date Block week Unit/Lesson/Topic sheet physics 9 8/9/2024 1 1-5 Unit 1: Waves, light and sound Study Learning Distinguish between transverse and longitudinal waves and be Outcome: able to give suitable examples of each Describe the longitudinal wave. Describe the transverse wave. Define wave as a vibration that transfers energy Define wavelength, frequency and amplitude Differentiate between transverse and longitudinal waves Sort examples of wave to longitudinal and transverse Learning wave objectives: Draw longitudinal wave with labelling amplitude and wavelength Draw transvers wave with labelling amplitude and wavelength Show understanding of seismic waves as an example showing that refraction and reflection take place with all types of waves What is meant by " A wave"? A wave is any disturbance that transmits energy through matter or empty space. Waves are vibrations that transfer energy from place to place without matter (solid, liquid or gas) being transferred. The energy passed along by a wave moves farther and farther from the source of energy, the direction of transferring energy is known as “wave direction” waves can be categorized to mechanical or electromagnetic waves 1. Waves that need medium to travel through are mechanical waves like sound 2. Wave that do NOT need medium to travel through (can travel through space) are electromagnetic waves like light Also they can be categorized to longitudinal and transverse Transverse waves In transverse waves, the oscillations are at right angles to the direction of travel and energy transfer. Transverse waves are made up of crests and troughs. The high point of a transverse wave is a crest. The low point of a transverse wave is a trough pg. 2 Light and other types of electromagnetic radiation are transverse waves. All types of electromagnetic waves travel at the same speed through a vacuum, such as through space. Water waves and S waves are also transverse waves. Longitudinal waves In longitudinal waves, the oscillations are along the same direction as the direction of travel and energy transfer. Sound waves and waves in a stretched spring are longitudinal waves. P waves are also longitudinal waves. Longitudinal waves show areas of compression and rarefaction. In the slideshow below, the areas of compression are where the parts of the spring are close together, while the areas of rarefaction are where they are far apart. Seismic waves: There are two broad classes of seismic waves: body waves and surface waves. pg. 3  Body waves travel within the body of Earth. They include P waves (primary) and S waves (secondary). P-waves: P waves cause the ground to compress and expand, that is, to move back and forth, in the direction of travel. They are called primary waves because they are the first type of wave to arrive at seismic recording stations. P waves can travel through solids, liquids, and even gases. S-waves: S waves shake the ground in a shearing, or crosswise, motion that is perpendicular to the direction of travel. These are the shake waves that move the ground up and down or from side to side. S waves are called secondary waves because they always arrive after P waves at seismic recording stations. Unlike P waves, S waves can travel only through solid materials. pg. 4 Wave parameters The various parts of a wave are described below: Wavelength(λ) The distance from one point on the wave to the same point on the next wave. Or from a center of compression to the center of the next compression Wavelength is measured in metres (m) and has the symbol λ. Frequency(F) This is the number of waves produced in 1 second by the source producing the wave. Frequency is measured in Hertz (Hz) and has the symbol f. Amplitude (A) The maximum displacement that an oscillation or wave has from its rest position. Amplitude is related to the energy of the wave: large-amplitude sounds are louder; large-amplitude light waves are brighter. pg. 5 Subject Grade Date Block week Unit/Lesson/Topic sheet physics 9 8/9/2024 1 1-5 Unit 1: Waves, light and sound Study Learning describe the refraction of light and explain why this happens in terms of the Outcome: speed of light and the density of the object it is travelling through Identify the refraction phenomenon State the conditions of light refraction Label light refraction diagrams with angle of incidence, angle of refraction and normal line Draw the normal lines onto light refraction diagram and measure the Learning angles of incidence and refraction objectives: Complete the drawing of light refraction from rare density to denser media and vice versa. Relate the relationship between the angle of incidence and angle of refraction to the speed of light and density of different media Explain the formation of mirages using the light refraction concept Investigate the refraction using different apparatus pg. 6 What is meant by light reflection? When a ray of light approaches any surface and the light ray bounces back, it is called the reflection of light. Light reflection: It is the bouncing back of a light ray when it falls on a reflective surface The law of reflection When light reaches a mirror, it reflects off the surface of the mirror: the incident ray is the light going towards the mirror the reflected ray is the light coming away from the mirror In the ray diagram: the hatched vertical line on the right represents the mirror the dashed line is called the normal, drawn at 90° to the surface of the mirror the angle of incidence, i, is the angle between the normal and incident ray the angle of reflection, r, is the angle between the normal and reflected ray The law of reflection states that the angle of incidence equals the angle of reflection,i = r. It works for any angle. For example: the angle of reflection is 30° if the angle of incidence is 30° the angle of reflection is 90° if the angle of incidence is 90° Note: If a light ray travelling along the normal hits a mirror, it is reflected straight back the way it came. In this case the angle of incidence = angle of reflection = 0° pg. 7 Refraction Light waves change speed when they pass across the boundary between two substances with a different density, such as air and glass. This causes them to change direction, an effect called refraction. Light refraction: changing the direction of a light ray when it passes through two different transparent media (with different optical densities). (this is due to the change of light speed) At the boundary between two transparent substances: the light slows down going into a denser substance, and the ray bends towards the normal the light speeds up going into a less dense substance, and the ray bends away from the normal The diagram shows how this works for light passing into, and then out of, a glass block. The same would happen for a Perspex block: The relation between the optical density of a medium and the speed of light through it. Optical density is a measure of how fast or slow the light propagates (travels) through a medium. The more optical dense a material, the slower light travels through it pg. 8  The normal Is a line drawn perpendicular to the boundary at the point of incidence. The incident ray Is a ray that shows the direction that light travels as it approaches the boundary The angle of incidence The angle that the incident ray makes with the normal line The refracted ray Is a ray that shows the direction that light Travels after it has crossed over the boundary The angle of refraction The angle that the refracted ray makes with the normal line The direction of bending: When light travels from rarer to denser When light travels from denser to rarer medium , it slows down. medium, it speeds up. It bends towards the normal. It bends away from the normal Angle of incidence > Angle of refraction I > R Angle of incidence < angle of refraction I < R What if the incident light ray falls perpendicular on the separating surface?! It passes without changing its direction pg. 9 Refraction and Sight: Light reflected off the coin is refracted away from the normal as the ray leaves the water, in order for your eye to see the coin. Therefore the coin's position appears to be shallower than it actually is. It also appears magnified adding to the perception of being closer. Your brain assumes that the light travelled in a straight line You brain forms the image at the place where it thinks the rays have come from. So the coin appears to be higher than it really is. pg. 10 Subject Grade Date Block week Unit/Lesson/Topic sheet physics 9 8/9/2024 1 1-5 Unit 1: Waves, light and sound Study describe total internal reflection, including the term critical angle, and Learning provide some examples of where this has practical applications, such as Outcome: with optical fibres. State the conditions of total internal reflection Draw a diagram of total internal reflection with label of critical angle. Explain how optical fibers work as an application for total internal reflection State the importance of total internal reflection in the transmission Learning of high-speed data along optical fibers in the form of pulsing laser objectives: light Identify uses and applications of fiber optics, including such uses as cable telecommunications and endoscopes Investigate the refraction and total internal reflection using different apparatus pg. 11 Total internal reflection: When light speeds up as it passes from a Slow to a Fast medium (more dense to less dense), the angle of refraction is bigger than the angle of incidence. For example, this happens when light passes from water to air or from glass to water. At any angle of incidence greater than the critical angle, the light cannot pass through the surface - it is all reflected. This is called total internal reflection. Two Requirements for Total Internal Reflection: 1- The light is in the more dense medium and approaching the less dense medium. 2- The angle of incidence is greater than the critical angle pg. 12 Optical fibres: An optical fibre is a flexible, transparent fibre made by drawing glass (silica) or plastic to a diameter slightly thicker than that of a human hair. Very little light is absorbed in the glass. Light getting in at one end is totally internally reflected, even when the fibre is bent. Usage of optical fibres: 1- Communication Optical fibres have become very important in high-speed communications, such as cable TV and highspeed broadband services. 2- Endoscope An endoscope is an instrument used in medicine to help examine the inside of the body, which uses bundle of optical fibre to transmit the image around corners. pg. 13 Subject Grade Date Block week Unit/Lesson/Topic sheet physics 9 8/9/2024 1 1-5 Unit 1: Waves, light and sound Study Learning know that a prism can split white light by refraction into its constituent Outcome: colours, recall these colours and know this is called dispersion Recall the spectrum colors. Learning Identify what is meant by dispersion process objectives: Investigate components of white light by refraction of light through prism. Use prism to split whit light into seven spectrum colors Light dispersion When white light passes through a prism, it is dispersed and the different colours of the spectrum separate. Dispersion causes rainbows. Red Orange Yellow Green Blue Indigo Violet(ROYGBIV) Dispersion happens because the different spectral colours travel at the same speed in a vacuum, but at different speeds in a medium such as glass. The amount of bending increases as the change in wave speed increases. pg. 14 Dispersion For dispersion in a medium such as glass: Each spectral colour has a different speed. Violet light refracts (bends) more than Red light, because Red light is the fastest in the medium. NOTE that: The refraction of light take place towards the base Converging lenses What is meant by a lens? A lens is a shaped piece of transparent glass or plastic that refracts light. When light is refracted it changes direction due to the change in density as it moves from air into glass or plastic. Lenses are used in cameras, telescopes, binoculars, microscopes and corrective glasses. pg. 15 Parallel light rays that enter the converging lens converge (collected). They come together at a point called the principal focus (focal point). Important definitions Optical center (O): the center of the lens Focal point: it is the point at which parallel rays are converged Focal length: it is the distance between the focal point and the optical center (C) Principal axis: is an imaginary line at 90 degree to the face of the lens, and passes through its optical center The images formed by the lens can be (its characteristics) Upright or inverted (upside down compared to the object) Magnified or diminished (smaller than the object) Real or virtual A real image is an image that can be projected onto a screen. A virtual image appears to cam from behind the lens (can’t be received on a screen). pg. 16 Subject Grade Date Block week Unit/Lesson/Topic sheet Physics 9 8/9/2024 1 1-5 Unit 1: Waves, light and sound Study Learning use practical apparatus to draw simple ray diagrams to show reflection, refraction and Outcome: total internal reflection, as well as the formation of a real image with a converging lens Draw a diagram showing dispersion of white light through prism Draw ray diagrams and use the normal line, angles of incidence and angles of refraction. Rearrange the seven colors of spectrum Investigate what happens to the dispersion of white light when the angle of incidence is changed. Relate the formation of the spectrum colors to the idea that angle of refraction Learning depends on objectives: wavelength as well as on the angle of incidence Investigate the reflection, refraction and total internal reflection using different apparatus. Describe how different optical apparatus work such as: binoculars, pinhole camera Plan investigation for the properties of image formed with converging lens. Draw the ray diagram of forming real image with a converging lens. Draw ray diagrams and use the normal line, angles of incidence and angles of refraction. pg. 17 Drawing a ray diagram for the image formed by a converging lens. we will investigate the method for drawing ray diagrams for objects placed at various locations in front of a convex lens. To draw these ray diagrams, we will have to recall the three rules of refraction for a convex lens. pg. 18 Life application for lenses: Human Eye Pin-hole Camera Projectors Cinemas pg. 19 Subject Grade Date Block week Unit/Lesson/Topic sheet physics 9 8/9/2024 1 1-5 Unit 1: Waves, light and sound Study Learning describe what ultrasound is and describe its common applications. Outcome: Identify the meaning of ultrasound. Discuss the application of ultrasound. Apply the formula of speed of wave to calculate the depth of sea Compare between frequencies of different sound waves. State different application of ultrasound in life as Learning o ultrasonic distance measurement by echo objectives: o medical scans in pregnancy o medical treatments o Silent dog whistle o Ultrasonic cleaning use of sonar to find fish Calculate the distance under sea using the formula of speed of wave pg. 20 Ultrasound waves The range of human hearing is about 20 Hz to 20,000 Hz. Ultrasound waves have frequencies above about 20,000 Hz (which is 20 kHz). As this is above the normal hearing range for humans, we cannot hear ultrasound. Ultrasound can be produced by some animals (such as bats and dolphins), as well as by some electronic devices. Applications in medicine. These include: Checking the condition of a fetus Investigating liver, heart problems Breaking down kidney stones and stones elsewhere in the body Measuring the speed of blood flow in the body Medical images from ultrasound The ultrasound is sent into the patient's body. At each boundary between different tissues or organs some of the ultrasound is reflected. The reflected waves (echoes) are usually processed to produce a picture of the inside of the body on a screen. The ultrasound waves used to image babies and soft tissue organs have small amplitude so are low energy. This makes it safer for the patient, as no damage is done to any living cells. Breaking down kidney stones and stones elsewhere in the body A high-powered ultrasound wave is used to break down kidney stones and other stones in the body. The stones vibrate until they shake themselves apart and are then easily passed out of the body. Ultrasonic distance measurement by echo e.g. to find the depth of the ocean floor. When ultrasound waves reach a boundary between two substances with different densities, they are partly reflected back. The remainder of the ultrasound waves continue to pass through. A detector placed near the source of the ultrasound waves is able to detect the reflected waves. It can measure the time between an ultrasound wave leaving the source and reaching the detector. The further away the boundary, the longer the time between leaving the source and reaching the detector: distance (metre, m) = speed (metre/second, m/s) × time (second, s) pg. 21 For example, sound travels through water at about 1,400 m/s. If it takes 0.5 s for a sound to reach a boundary and reflect back to the detector, the total distance travelled is: distance = speed × time = 1,400 × 0.50 = 700m The distance to the boundary is half this, which is 350 m. The distances and times are much smaller of course when scanning babies and in engineering jobs. Silent dog whistle Is a type of whistle that emits sound in the ultrasonic range, which people cannot hear but some other animals can, including dogs and domestic cats, and is used in their training. Ultrasonic cleaning pg. 22  Mind maps for revision pg. 23 pg. 24 pg. 25 simulations and important links http://www.physicslessons.com/demos.html#light https://phet.colorado.edu/sims/html/sound-waves/latest/sound-waves_all.html https://phet.colorado.edu/sims/html/color-vision/latest/color-vision_all.html https://phet.colorado.edu/en/simulations/geometric-optics https://phet.colorado.edu/en/simulations/waves-intro https://phet.colorado.edu/en/simulations/bending-light https://phet.colorado.edu/sims/html/waves-intro/latest/waves-intro_en.html https://www.walter-fendt.de/html5/phen/ https://phet.colorado.edu/en/simulations/wave-on-a-string pg. 26