4.6 Waves Flashcards
(30 cards)
What is a transverse wave?
A wave in which the oscillations are perpendicular to the direction of energy transfer; examples include light and water waves.
What is a longitudinal wave?
A wave in which the oscillations are parallel to the direction of energy transfer; an example is a sound wave.
What are the key features of a wave?
Amplitude (height from rest), wavelength (distance between peaks), frequency (waves per second), period (time for one wave), and wave speed.
What is the equation for wave speed?
Wave speed = frequency × wavelength (v = f × λ).
How is the period of a wave calculated?
Period = 1 ÷ frequency (T = 1/f).
What is reflection?
The bouncing back of a wave at a boundary; the angle of incidence equals the angle of reflection.
What is refraction?
The bending of a wave as it passes from one medium to another due to a change in speed.
What is the electromagnetic spectrum?
The range of all electromagnetic waves, from radio waves (longest wavelength, lowest frequency) to gamma rays (shortest wavelength, highest frequency).
What are the uses of radio waves?
Radio and TV communications; they are transmitted easily over long distances and through the atmosphere.
What are the uses and dangers of microwaves?
Used for satellite and mobile phone communication and cooking; can cause internal heating of body tissues.
What are the uses and risks of infrared radiation?
Used in heaters, night vision equipment, and remote controls; excessive exposure can cause skin burns.
What are the uses and risks of visible light?
Used in photography, communication (optical fibres), and illumination; high-intensity light can damage the eyes.
What are the uses and risks of ultraviolet (UV) radiation?
Used for sterilisation and detecting forged banknotes; can damage skin cells and cause skin cancer.
What are the uses and dangers of X-rays?
Used in medical imaging to view bones; exposure must be limited due to risk of cell damage and cancer.
What are the uses and dangers of gamma rays?
Used for sterilising medical equipment and cancer treatment (radiotherapy); very penetrating and can damage DNA and cells.
How are electromagnetic waves produced?
They are generated by changes in atoms and nuclei, such as electrons changing energy levels or radioactive decay.
What is a concave lens and what does it do?
A lens that curves inward and causes parallel rays to diverge (spread out).
What is a convex lens and what does it do?
A lens that curves outward and causes parallel rays to converge (come together).
What is a real image?
An image formed when light rays converge and can be projected on a screen.
What is a virtual image?
An image that cannot be projected as the light rays only appear to come from a position (e.g., image in a mirror).
What happens to sound waves as they travel through different media?
Their speed changes depending on the medium, but frequency remains constant; they can reflect, refract, or be absorbed.
How does the ear detect sound?
Sound waves cause the eardrum to vibrate, which is transmitted through the middle ear bones to the cochlea, converting it into electrical signals.
What happens when sound waves enter a denser medium?
They speed up, and their wavelength increases, but the frequency stays the same.
How can ultrasound be used?
Medical imaging (e.g. prenatal scans), detecting cracks in materials, and sonar.
