Grade 10 Science Reviewer

Thomas Young – provided the first experimental evidence for a wave theory of light through his double-slit interference experiment James Clark Maxwell – provided a convincing wave description of light and other forms of electromagnetic radiation. Electromagnetic wave – an electrical and magnetic disturbance that moves through space at the speed of light (c = 3.0 x 10^8 m/s) - Combined field of electric and magnetic nature/field - Produced by the oscillating charge on the antenna - Also known as Electromagnetic Radiation  Electricity and Magnetism can both be static. Types of Electromagnetic Waves:  Radio Waves – used mostly for communication  Microwaves – used for radar tracking, radio navigation, communication, medical diathermy, heating in microwave ovens, drying, and other industrial purposes  Infrared Waves – heat or thermal radiation - Causes the amplitude of vibration of molecules in your skin to increase  Light Waves – caused by the motion of electrons in atoms - starts with red light and ends with violet light  Ultraviolet Radiation – darkens the skin  X-rays – used for examining the interior objects that are opaque to light  Gamma Rays – produced by the motion of charged particles in nuclei.  energy increases  wavelength decreases  frequency increases  Inverse relationship - frequency & wavelength, wavelength & energy  Direct relationship – frequency & energy Mechanical Waves Electromagnetic Waves Need a material medium do not need a material for their propagation medium for their propagation they travel through a vacuum caused by wave Are due to change in amplitude and not by electric and magnetic frequency fields Considered periodic Are just called disturbances disturbances Have low speed Have high speed Cannot undergo Can be polarized polarization Frequency – number of complete vibrations per second of the field at a point along the path of the passing wave. - Also is equals to the vibration frequency of the wave‟s source.  EM wave depends on its frequency and speed. Band – particular range of wavelengths Electromagnetic Spectrum – radiation energy that travels and spreads out as it goes Photon – bundle of energy

Radio Waves  Longest wavelengths  Lowest frequency  Highest energy  Radio Detecting and Ranging (RADAR) – to find position and speed of objects by bouncing radio waves  Magnetic Resonance Imaging (MRI) – 1980‟s, to diagnose illness  AM radio – KHz  FM radio – MHz  James Clerk Maxwell – showed mathematically that electromagnetic waves could propagate through free space. Microwaves  Have very short wavelengths  Can be found between very high frequency (infrared) waves and conventional radio waves.  Transmitter – electronic device, which with the aid of an antenna, produces radio waves  Used in telecommunication such as mobile phones  Used in satellite communication, radar, mobile phones, and for cooking Infrared  Sir William Herschel – discovered in 1800 the existence of infrared by passing sunlight through a prism.  Spectrum – a rainbow colors  Has longer wavelength than that of visble light  Emitted or absorbed by molecules  Used to remotely determine the temperature of objects  Known as thermography or pyrometry  Used in:  Taking pictures of big views  Show temperature variation of the body  Remote controllers  Telescopes for seeing in the dark  Autofocus cameras (infrared pulses) Visible Light  Portion of EM radiation that is visible to the human eye  Given off by anything that is hot enough to glow.  We see them as the colors of the rainbow  Red has the longest wavelength  Violet has the shortest wavelength  White – combination of all the color  Black – absence of light Ultraviolet  Has shorter wavelength than that of visible light  Produced by high-temperature surfaces  Ultraviolet radiation in sunlight is absorbed by oxygen  Non-ionizing Radiation – any type of electromagnetic radiation that does not carry enough energy per quantum to ionize atoms or molecules.  Too much Ultraviolet may lead to skin cancer.

 UVA – longest  UVB – shortest  Used in Stillwater, lamps in bank, paints that glow in sunlight X-rays  High-energy waves which have great penetrating power and are used extensively in medical applications and in inspecting welds  Called as Röntgen Radiation, named after Willhelm Conrad Röntgen – discoverer of xray  Has short wavelengths Gamma Rays  More penetrating than X-rays  Has high energy waves  From nuclear reactions  Has shortest wavelengths  Used in sterilizing medical instruments  Used to kill cancer (kill the cancerous cells)  Non-ionising are less harmful than Ionising Non-ionising – ranges from radio to UVA Ionising – ranges from UVB to gamma rays Electromagnetic Radiation / Radiant Energy – the energy produced by nuclear reactions at the core of the sun Radiation – the process of emitting energy by 2 basic carriers:  Particles – high-energy protons, neutrons, electrons, atoms, and ions  Waves – light or sound Classifications of Radiation:  Natural or Background Radiation  Radon – a radioactive gas from uranium found in soil dispersed in the air  From radioactive potassium in our food and water  From uranium, radium, and thorium in the earth‟s crust  From cosmic rays and the sun  Man-made Radiation  Includes: Tobacco, television, medical X-rays, smoke detectors, lantern mantle, nuclear medicine, and building materials  Ionizing Radiation – can create electrically charged ions in the material it strikes. - can break apart atoms and molecules  X-rays and Gamma Rays – highenergy parts of EM spectrum  Cosmic Radiation – energetic particles arriving on Earth from outer space  Neutrons – produced mainly in nuclear power plants  Internal Hazards: Alpha Particles – Atomic nuclei (2 protons and 2 neutrons) Beta Particles – Fast-moving electrons ejected from the nuclei of atoms  Non-ionizing Radiation – harmless, does not carry enough energy per quantum Radiation – changes in the state of an atom

Gamma Rays – produced when the nucleus of the atom changes state Cosmic Radiation – comes from both inside and outside the Solar System Sources of Ionizing Radiation:  Radon (Background Radiation) – natural sources  Variety of Human Activities – example: nuclear power plant Effects of Radiation to Humans:  Eye and skin damage – may lead to cataracts, glaucoma, or skin cancer  Result in cancer  Sickness and death  Genetic Mutations 1. Stochastic Effects – long-term, low-level exposure to radiation 2. Non-stochastic Effects – high levels of radiation and became more severe as the exposure increases. Plato – thought that light consisted of streamers emitted by the eye Pythagoras – light originated from luminous bodies in the form of very fine particles Empedocles – light is composed of high-speed waves of some sort. 2 Theories on the Basic Nature of light: 1. Wave (Undulatory) Theory – light has a wave motion that starts from a vibrating body and is transmitted at high speed. Christian Huygens – explained the reflection of light using wave motion - Proposed that light consists of series of waves with their wave fronts at right angles to the path of the rays. Huygen’s Principle – different points of a wave front of light set up a series of secondary waves. Ether – a medium, a mysterious substance which is not air. (light may travel through a medium) 2. Corpuscular (Emission) Theory – light consists of tiny particles of matter emitted by a source that travel only in straight lines – rays Isaac Newton – described light as a stream of particles corpuscles. Thomas Young – was able to study the interference and diffraction (wave) of light James Clerk Maxwell – constructed an oscillating electrical circuit, which showed that changing electric and magnetic fields could produce electromagnetic radiation that could travel through a vacuum. Heinrich Hertz – demonstrated the existence of electromagnetic waves (within radio frequency) that exhibit the same properties as the light. Max Planck – hypothesized that the vibrating electrons in incandescent lights could only have energies restricted to certain values. Blackbody Radiation – emitted in discrete bundles of energy, introduced by Max Planck Quanta (Quantum) - bundles of energy Quantum Theory of Light (Max Planck)  Albert Einstein – states that light is composed of bundles of wave energy Photons – bundles of wave energy

 In latter part, scientists observed that light was capable of ejecting electrons Photoelectric Effect – if light falls on a clean surface of metals such as potassium or sodium, electrons are emitted by the surface Arthur Compton – studied the scattering of X-rays by electrons all required the assumption of a particular nature for electromagnetic radiation without in any way invalidating the wave theory of light Louis Victor de Broglie – proposed that every particle of matter is somehow endowed with a wave to guide it as it travels. Galileo – first to hypothesized that light had a finite speed  The immense speed of light calls for the measurement of its passage  There was no way for Galileo to prove his theory in his lifetime Ole Roemer – a Danish astronomer, became the first person to measure the speed of light over an astronomical distance Light – speed of 220 million m/s Albert A. Michelson – conducted that the speed of light in empty space at c as 2.9979 x 10^8 m/s Optics – branch of physics, which involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Light Source: 1. Luminous Objects – objects that emit or send off their own light - Tend to radiate heat as an effect of being luminous and can store energy. 2. Non-luminous Objects – objects that cannot emit their own light - Illuminated objects Light Produced: 1. Incandescence – object is heated at a very temperature, it starts to glow and become dull red in color 2. Luminescence – process by which light is produced other than by heating  Fluorescence – release of light that lasts no more than about 10 nanoseconds (fluorescent light bulb)  Phosphorescence – release of light that lasts longer than 10 nanoseconds (glow-in-the-dark) Transparency 1. Transparent – permit the passage of light 2. Opaque – block light 3. Translucent – allow only some amount of light to pass through - Have both the characteristics of opaque and transparent materials  Rays from the source travel radially but when obstructed by opaque materials, shadow is produced. Shadow – the region behind an opaque object from which light is blocked or cut off.  Umbra – total shadow  Penumbra – partial shadow, not equally dark Fermat’s Principle – „in going from one location to another, light will take the most efficient path that is the path that requires the shortest time, provided

that there is nothing to obstruct the passage of the light.‟ (Pierre de Fermat) Photometry – branch of optics that deals with illumination and the amount of brightness that a light source possesses. Luminous Intensity – refers to the brightness of a light source Candela (cd) – unit expressed  The brighter the light source is, the greater is its luminous intensity. Luminous Flux – luminous energy wmitted from a light source. (Lumens lm) Light – electromagnetic radiation that has properties of waves and particles. Echo – reflected sound wave Reflection – Light waves also bounce off from a reflecting surface Law of Reflection – “the angle of incidence is equal to the angle of reflection as measured from the normal line, which is the line drawn perpendicular to the surface of the mirror.”  Incident ray  Reflected ray  Normal line Reflection of Light: 1. Specular (regular) – occurs when the reflective surface is very smooth 2. Diffuse (irregular) – when light hits a rough surface, resulting to the bouncing back of light waves in different directions. Diffusion – the dispersal of reflected light Absorption – the transfer of energy carried by the light waves to the particles of matter. Scattering – the reflection of light by particles. Refraction – bending of light as it passes from one medium to another.  Water – 2.25 x 10^8 m/s Index of Refraction – the ratio of velocities of light as it passes from a vacuum into another medium  C – speed of light in vacuum V – speed of light in another medium Critical Angle – an angle of refraction that is equal to 90 degrees in the medium. Total internal reflection – the incident rays striking the boundary of 2 media are reflected back into the first medium and the bounding surface act like a perfect reflector Dispersion – effect associated with the separation of light into colors by prism. Diffraction – bending of light as it passes around the edge of a barrier. - Sometimes called as Scattering Interference of Light / Optical Interference – when 2 light waves from different coherent sources meet together, the distribution of energy due to one wave is disturbed by the other. Fringe – a dark or light band Interference of Fringes – bands of color Diffraction Pattern – the pattern on the screen, when only one slit is open Constructive Interference – when 2 or more waves come together to form a larger and stronger wave, matching their crest and troughs (light bands)

Destructive Interference – when 2 or more waves‟ crest coincide with the waves‟ troughs, the waves cancel each other out. (dark bands) Polarization – the orientation of their vibrations - Undergo polarization Polaroid Filter - polarizer Image – formed when light strikes a reflecting surface such as a mirror or lens. Object – actual Image – picture you see in the mirror Real Images Virtual Images Light rays actually Light rays do not meet intersect at the image at the image Appear inverted, or Appear erect, or right upside down side up (upright) Plane mirrors – the common, everyday flat mirrors - Flat, 2d surface that reflects the light coming from or reflecting off another object.  The image is upright, but left-right reversed Law of plane mirrors – “the image is always the same distance behind the mirror as the object is in front of the mirror” Law of Reflection – “the angle of incidence equals the angle of reflection” - Observed when reflecting surface is smooth Spherical Mirror – second class of mirror in the form of a slice of a spherical surface. A. Concave Mirror – mirror that is curved inward. - Either virtual or real B. Convex Mirror – mirror that is curved outward. - Virtual image Features of a concave and a convex mirror: a. Center of Curvature – center of the circle of which the mirror represents a small arc b. Focus – point where parallel light rays converge, found on the „inner part of the circle‟. 1/2R c. Vertex – point where the mirror crosses the principal axis d. Principal Axis – a line drawn through the vertex, focus, and center of curvature of the mirror upon which the object rests. e. Focal Length – the distance from the focus to the vertex of the mirror f. Radius of Curvature – distance from the center to the vertex of the mirror, it corresponds to the radius of the circle. Pppppppiiiiiiccccttttuuuuuurrrrreeeee Principal Ray – ray that leaves a point on an object facing the mirror parallel to the principal axis. Focal Ray – ray that leaves the same point on the object and immediately passes through the focal point. Chief Ray – ray that leaves the same point on the object and passes through the center of curvature of the mirror. Mirror Equation – expresses the quantitative relationship between the object distance, the image distance, and the focal length. Magnification Equation – the ratio of the image distance and object distance to the ratio of the image height and object height.