RI 2017 Physics Notes

2017 Physics EOY 1. Measurement Actual reading = observed reading - zero error Procedures to make readings more accurate 1. Obtain three or more readings at different positions and take the average. 2. Check and correct for any zero errors Ratchet - Prevent over tightening of the micrometer screw gauge PREFIXES Tera T 1 0 1 2 Giga G 1 0 9 Mega M 1 0 6 Kilo k 1 0 3 Hecta h 10 ​ 2 Deka da 10 ​ 1 Deci d 1 0 − 1 Centi c 1 0 − 2 Milli m 1 0 − 3 Micro μ 1 0 − 6

Nano n 1 0 − 9 Pico p 1 0 − 1 2 SI UNITS Length Metre m Mass Kilogram kg Time Second s Electric Current Ampere A Temperature Kelvin K (0K = -273°C) Amount of Substance Mole mol Luminous Intensity Candela cd Speed Meter per Second m/s Acceleration M e t e r p e r S e c o n d 2 m / s 2 Weight Newton N or kgm/s ​ 2 Volume Cubic Centimeter c m 3 Moments Newton Meter Nm Work Done / Energy Joules J or kgm ​ 2 ​ /s ​ 2 Gravitational force Newton per Kilogram N / Kg Frequency Hertz Hz Wavelength Metre (lambda) m (symbol: 人 ) E.M.F / Voltage / P.D Voltage V Resistance Ohm Ω Resistivity Ohm Meter • m Ω Area Metre ​ 2 m 2 Pressure Pascal Pa

Scalar Quantity Vector Quantity Distance Displacement Speed Velocity Temperature Acceleration Mass Weight Density Force Energy Turning Moments Power Time 2. Mass, Weight & Density w = mg (weight = mass x gravitational pull) p = (density = mass / volume) m V Inertia - The property of a mass which resists change from its state of rest or motion of body Weight - The amount of gravitational field acting on a mass 3. Reflection Luminous objects - objects that give off light on its own (eg: Sun, Lamps) Non-Luminous objects - objects that are seen when they reflect light from a source (the moon is a non-luminous object!!!!!!!) Two laws of Reflection (true for ALL REFLECTING surfaces, including curved mirrors, and uneven / rough surfaces) The first law states that the angle of incidence, i, is equal to the angle of reflection, r. (i=r) The second law states that the incident ray, the reflected ray, and the normal to the surface of the mirror all lie in the same plane. *Normal - perpendicular line to the reflecting surface - When a light falls on an uneven surface, ​ individual ​ light rays still obey the laws of reflection. It is the overall image that is diffused.

Characteristics of a plane mirror image 1. The image is the same size as the object 2. It is laterally inverted 3. It is upright 4. It is virtual 5. Its distance from the mirror is equal to the distance of the object from the mirror Applications of Reflection 1. Periscope - Used to look over high obstacles - Consists of 2 plane mirrors inclined at an angle of 45 ​ ° - Second mirror reverses the lateral inversion caused by the first mirror, causing the final image to appear without lateral inversion Mirror in a Meter (Voltmeter, Ammeter) - Adjust the position of your eye until the image of the pointer cannot be seen / the image is directly below the pointer, then read the reading to avoid parallax error. Other Uses of Reflection in Our Daily Lives: - Dentist mirror - Rear view mirror - Security mirror in shop - Torchlight - Cosmetic mirror - Decorative mirror 4. Refraction - Occurs when light travels from one medium to another n = (air to glass) s i n i s i n r n = (glass to air) s i n i s i n r n = (C = critical angle) 1 s i n c n ​ 1 ​ sinθ ​ 1 ​ = n ​ 2 ​ sinθ ​ 2 n = (where c is the ​ speed of light in vacuum 3.0 x 10 ​ 8 ​ ms ​ -1 ​ ​ and v is the speed of light in medium) v c n = (with respect to air) R e a l d e p t h A p p a r e n t d e p t h Note: Refractive index ​ n ​ will always be bigger than or equal to 1 Two laws of Refraction The first law states that the incidence ray, the normal and the refracted ray all lie in the same plane. The second law states that for two given media, the ratio of the sine of angle of incidence ​ i ​ to the sine of angle of refraction is a constant, ie = constant. This is also known as Snell’s Law. s i n i s i n r When the angle of incidence is 0 ​ o ​ , refraction does not occur Critical angle ​ c ​ is defined as the angle of incidence in an optically denser medium for which the angle of refraction is the optically less dense medium is 90 ​ o n = 1 s i n c

Total internal reflection is the complete reflection of a light ray inside an optically denser medium at its boundary with an optically less dense medium. The two conditions for total internal reflection are 1. The light ray in an optically denser medium strikes its boundary with an optically less dense medium. 2. The angle of incidence is greater than the critical anger of the optically denser medium. Why are refracted rays not as bright as incidence rays? When light strikes the air glass boundary, part of the incident ray is reflected away at an angle of reflection equal to the angle of incidence. Hence only part of the ray is refracted, hence it is not as bright Summary: I < C - refraction I = C - ray is refracted along the surface of object I > C - total internal reflection occurs Fiber Optics (Application of TIR) - ‘light pipes’ used to transmit light from one place to another - light entering the pipe comes out from the pipe because of total internal reflection from the sides - images can be transferred from one point to another Why does light not escape from the sides of the optical fibre? The optical fibre has high optical density, thus from the equation n = , it will have a small critical angle. When 1 s i n c the angle of incidence is larger than the critical angle and travelling from an optically denser medium to an optically less dense medium, light undergoes total internal reflection. Light Bending 1. From air to glass, angle of incidence is bigger than angle of refraction (refracted ray bends towards the normal) 2. From glass to air, angle of incidence is smaller than angle of refraction (refracted ray bends away from the normal)

5. General Wave Properties v = fλ (speed = frequency x wavelength) T = f 1 f = 1 T Transverse waves propagates in a direction / movement of each particle is perpendicular to the direction of vibration Longitudinal waves propagates in a direction / movement of each particle is parallel to the direction of vibration Note: If displacement is negative, include the negative sign Displacement Distance graph - shows displacement of all particles at a particular point in time Displacement time graph - shows displacement of one particle at a particular point in time 6. Electromagnetic Waves No. Property 1. Electromagnetic waves are transverse waves. They comprise electric and magnetic fields that oscillate at 90 ​ o ​ to each other. 2. They can travel through vacuum and do not require any medium to travel from one point to another 3. They transfer energy from one place to another. E.g transferring heat energy from sun to Earth 4. They travel at the same speed of light (3.0 x 10 ​ 8 ​ ms ​ -1 ​ ) in vacuum with their respective frequencies and wavelengths 5. The wave speed equation v = fλ is applicable to all electromagnetic waves 6. When an electromagnetic wave travels from one medium to another, it’s: 1. Speed and wavelength changes 2. Frequency does not change Frequency only dependent on source of the wave E.g when light travels from vacuum to water, it’s speed decreases from 3.0 x 10 ​ 8 ​ ms ​ -1 ​ to 2.25 x 10 ​ 8 ​ ms ​ -1 ​ . Its wavelength also decreases, while its frequency