Physics gcse combined edexcel

• The speed of light is the maximum possible speed at which anything can travel.
• Newtons first law

  A moving object will continue to move at a constant speed and in the same direction or will remain stationary when the resultant force acting upon the object is 0N
• Newtons second law


  F=m x aWhen there's a resultant force acting on an object, the object will accelerate in the direction of the resultant force.
• Inertial mass


  Ratio of net force exerted on object to its acceleration
• terminal velocity


  the constant velocity of a falling object when the force of air resistance is equal in magnitude and opposite in direction to the force of gravity.
• Terminal velocity of a falling object(a sky diver)

  °At the start of his jump, the air resistance is small so the driver accelerates downwards as the gravitational force is the largest force°as his velocity increases, the air resistance increases°eventually, the air resistance will equal the gravitational force.The resultant force is zero so the diver is travelling at a constant velocity. This is the objects terminal velocity.
• Centripetal force


  A force which acts on a body moving in a circular path and is directed towards the centre around which the body is moving
• Newton's Third Law

  For every action there is an equal and opposite reaction
• conservation of energy


  a principle stating that energy cannot be created or destroyed, but can be transferred from one form of energy to another.
• 4 main ways energy can be transferred

  Mechanically - a force on the objectElectrically-a charge doing work done against distanceBy heating-energy transferred from a hotter to a colder objectBy radiation - energy transferred by waves
• Speed


  The distance an object travels per unit of time
• Reflection


  The bouncing back of a wave when it hits a surface through which it cannot pass.
• Refraction


  The wave passes out into a new material of a different density and changes direction and velocity
• Transmission


  The wave passes through the material and is not absorbed or reflected
• Absorption


  The wave disappears as the energy it is carrying is transferred to the materials
• medium


  Material through which a wave travels
• Interface

  Boundary between 2 materials
• Deep water is less dense than shallow water
• EM spectrum definition


  scale that shows different types of transverse light waves; range of frequencies & wavelengths
• EM spectrum


  Radio waves, microwaves, infrared, visible light, uv, x rays, gamma rays
• Frequency


  the number of complete wavelengths that pass a point in a given time
• Amplitude


  Displacement of wave from rest position to the trough
• Wavelength


  The distance between two corresponding parts of a wave
• wave velocity


  frequency x wavelength
• gamma rays


  Shortest wavelength, highest frequency
• radio waves


  Longest wavelength, lowest frequency
• Law of reflection

  the angle of incidence is equal to the angle of reflection
• Explain why refraction is not possible at every angle of incidence


  If the angle of incidence is equal to or greater than the critical angle, refraction won't take place
• critical angle


  the angle of incidence that produces an angle of refraction of 90 degrees
• total internal reflection


  the complete reflection of light by the inside surface of a medium
• Conditions for total internal reflection


  -The angle of incidence is greater than the critical angle-wave must be moving from a. More optically dense object to the less dense material
• Speed of light in a vacuum


  3.00 x 10^8 m/s
• visible light


  Electromagnetic radiation that can be seen with the unaided eyeOur eyes can detect certain frequencies of lightDifferent frequencies cause us to see different coloursLower frequencies appear more redHighest frequencies appear more blue.
• diffuse reflection


  Reflection that occurs when parallel rays of light hit a rough surface and all reflect at different angles
• specular reflection


  a reflection produced by a smooth surface in which parallel light rays are reflected in parallel
• Dangers of EM waves

  Radio waves - no harmful effectsMicrowaves-no health problems caused by microwavesInfrared-skin absorbs radiation, which we feel as heat - could cause burns if too much radiation is exposed to usVisible light-no health benefitsUv-sun, skin cancerX rays-mutation in dna causing cancerGamma rays-can penetrate the skin, causing mutations