Sensory pits in animals like the snake that can sense warm blooded animals due to their infrared emission.
Waves and sounds
Waves and sounds
What is a wave?- A wave is a disturbance that travels through a medium from one location to another- A wave is the motion of disturbance- The frequency of a wave is its most basic factor which doesn’t change when entering one medium through another.
-Mechanical waves are produced by a disturbance .-It requires a medium to travel. Common examples include air, water and sound.- There are 3 types: Transverse, Longitudinal and Surface
In transverse waves the direction of the disturbance is perpendicularTo that of the direction of travel of the wave.They also occur when the source disturbance of the wave follows aperiodic motion.They create crests and troughs while travelling and show polarization.
In this type of a mechanical wave the direction of disturbanceIs parallel to the direction of the motion of the waves.
Polarization : It is the process in which the wave vibrates inonly one plane.Reflection: When a wave gets reflected back upon enteringa medium is known as reflection.Refraction: When switching from one medium to anotherwhen the speed of the wave changes and not the frequency.Diffraction: The spreading of waves when it enters through asmall slit is known as diffraction.Wave fronts: It gives the position of the waves at a certaintime
Longitudinal waves Transverse waves• Vibrations parallel to • Vibrations at right direction of motion angle to the• They produce rare direction of motion. faction and • They create crests compression and troughs• They do no show • They do show polarization polarization.
The wavelength of a wave is the measure of one crest and one troughWhich Is represented by the Greek letter lambda.
A displacement – distance graph can also be used
• Light, microwaves, x-rays, and TV and radio transmissions are all kinds of electromagnetic waves. They are all the same kind of wavy disturbance that repeats itself over a distance called the wavelength.
At vacuum they travel with the speed of light, i.e at 300000000 m/s ; They show polarization and Diffraction , thus they are transverse in nature;they obey the general equation; they carry energy From one place toanother and can be absorbed by matter to cause heating and other effect
Radio waves are the waves with the longest wavelength and the lowestFrequency, they are used to carry sound, pictures and other informationOver a long distance, they are reflected by small electrically chargedParticles present in the ionosphere which makes long distance radioReception possible. We use them in our radios , phones and TV’s whichAll usually have antennae’s on them.
This comes next in the spectrum. Their most common use is in the microWave. They help in cooking the food, they are also used in mobile phonesAnd TV’s. They are used for radar detection. They are the only wavesWhich can penetrate light rain, haze, snow, clouds and smoke and canTherefore be used in space for taking images of the Earth. These can haveWavelengths measuring a few centimeters to a foot in length.
Infrared is emitted by all living organisms in large or small quantity, theycan have wavelengths as long as a pin or as short as a cell. The longerInfrared rays are thermal, i.e. we feel warm due to their emission.The short infrared rays on the other hands are used in devices such asThe remote control. They can also be used to cook food faster. We canTake infrared sensitive photos using special cameras.
These rays are what cause are skin tan and some extreme cases skinCancer, but they also produce vitamins. The sun emits these rays theMost. They may not be visible to our eyes but the bumblebee andOther likewise organisms can. They are also used to detect invisibleSignatures and causes fluorescent clothes to flouresce.
The most common use of these rays are in X-Ray machines, they canPenetrate objects like clothes to give images of the bones.
These are the rays with the shortest wavelengths and highest frequency.Gamma rays are used to kill cells, like the cancerous cells. They are alsoUsed to clean surgical instruments.
It is a type of longitudinal wave which cannot like light waves travelIn vacuum and is best transmitted by solids followed by liquids andGases. It displays properties of interference and diffraction.They are well reflected from hard and flat surfaces causing echo.If the surface is nearer than 15m than the echo joins up with the originalSound, this is called reverberation.
The speed of sound varies depending on the material it travels through.In:AIR(0 degree C ): 330m/s ( for rise of every 1 degree the speed increases by 0.61 m/s)WATER : 1400m/sCONCRETE : 5000m/sSTEEL : 6000m/sWe can find the speed using the general equation and to find theWavelength we can use the formulaWavelength = velocity /frequency
Hearing capacity of humans is sound waves of frequency with 20Hz to20,000 Hz.The 3 properties of sound waves are:1)Pitch – Directly proportional to the frequency2) Loudness – Directly Proportional to the amplitude3) Quality – No instrument except a tuning fork emits a pure note and They have a fundamental note mixed with other notes which are overtones and are exact multiples of the fundamental notes.Frequencies of sound waves above 20,0000 Hz are called ultrasonic, andObjects with speed slower than sound are called subsonic and vice versaAre called supersonic.
Q.1. Sound is faster in ? Explain-Air- Water- solid
Q. Suggest the properties of Sound that prove that it is a waveQ. What are the factors that affect the speed of sound in any mediumQ. If a nurse cleans the surgical instruments just before a surgery , which ray does she use?