S2 Flashcards
How do waves transfer energy
Waves transfer energy from one point to another using vibrations
Types of progressive wave
Transverse, a wave which travels perpendicular to the direction of wave travel
Longitudinal, a wave which travels parallel to the direction of wave travel
Examples of longitudinal waves
Sound waves and ultrasound waves
Transverse waves
Water and electromagnetic
Frequency
The complete number of oscillations generated per second, is represented by f and measured in hertz/Hz
Wavelength
The distance between successive particles which are at the same point in their paths at the same time and are moving in the same direction
Amplitude
The maximum displacement of particles in the wave train from their rest positions
Ultrasound/ultrasonic sound + uses
Sound waves above 20,000 hertz, humans can’t hear them
Used in medicine to measure foetal head diameter and in industry to detect defects in metals
Uses of sonar and radar
Sonar uses sound pulses to detect objects underwater
Radar uses electromagnetic pulses to detect aircrafts and ships
Electromagnetic spectrum
Radio waves
Microwaves
Infrared radiation
Visible light
Ultraviolet radiation
X-rays
Gamma rays
Results of overexposure from electromagnetic spectrum
Microwaves can cause internal heating of body tissues
Infrared radiation can cause skin burns
Certain ultraviolet wavelengths cause skin cancer
Large doses of radio waves can cause cancer, leukaemia and other disorders
X-Rays and gamma rays can cause cancer
Refraction through a spectrum
The greater change of speed the greater the refraction. Red is refracted the least so it’s slowed the least, violet is refracted the most so it’s slowed the most
Critical angle & total internal reflection
Below critical angle = reflected ray + weak refracted ray
At critical angle = reflected ray + refracted ray at 90 degrees
Beyond critical angle = strong reflected ray + no refracted ray
Difference between long sight and short sight
Long sight: Hyperopia Long Sight Convergence corrected by Lens Convex Converging, lens too weak eyeball too short
Short sight: Short Sight Diverging Myopia corrected by Lens Concave Diverging, lens too strong eyeball too long
Conductors vs insulators
Conductors have many free electrons while insulators have little to none
Conventional current
The theory that electrons flow from a negative terminal to a positive, this has been proven false
Charge equation
Charge (Coulombs) = Current x Time
Voltage equation
Voltage (Volts/V) = Current (Amperes/A x Resistance (Ohms/I)
Energy & power equations
Energy = Power x Time
Power = Current x Voltage
Flemming’s left hand rule
Hold the thumb and first two fingers of the left hand at right angles to each other with the First finger pointing in the direction of the Field and the seCond finger in the direction of the Current then the Thumb points in the direction of the Thrust
How is a star formed
- Stars are formed when gravitational attraction pulls together amounts clouds of hydrogen gas and dust (called nebulae).
- This matter is pulled together very high temperatures are created as the gravitational potential energy of the gas is converted to kinetic energy.
- Temperatures as high as 15,000,000 K are reached and at such temperatures nuclear fusion occurs. The hydrogen nuclei fuse together to form Helium nuclei.
- During nuclear fusion where light nuclei fuse together to form heavier nuclei a huge amount of energy is released. A star has started to form.
- As the clouds of dust and gas initially collapse, they may cause the cloud to spin and as the cloud becomes more dense the spin rate increases.
- As the core becomes hot it may separate from the spinning cloud, which then takes the shape of a flat spinning disc.
- The hot core becomes the sun and the outer gases condense to form asteroids which then gather together to form the planets and other orbiting bodies.
How might the centripetal force increase
The centripetal force will increase if;
The mass (m) of the object increases
The speed (v) of the object increases
The radius (r) of the orbit decreases
Fleming’s right hand rule
Hold the thumb and first two fingers of the right hand at right angles to each other with the First finger pointing in the direction of the field and the thuMb in the direction of the Motion of the wire then the second finger points in the direction of the induced Current
Equation for centripetal force
F = mv2/r
