How long is each oscillation

The vibration caused by a wave, just as a vibration caused by an elastic medium say, a spring , has an amplitude, a period, and a frequency. So, a wave also is characterized by its frequency, or period, and its amplitude. In addition, a wave is also characterized by its speed of travel. Another way of taking the wave speed into account is to instead refer to the distance that the wave travels to produce a full cycle of its vibration.

This distance is called the wavelength. As the wave moves by, in a time equal to the period one oscillation of the wave occurs and so the wave has moved along a distance equal to the wavelength. The velocity of the wave is then given by.

In the case of water waves, for example, the distance from the one peak to the next or one valley to the next is one wavelength see the figure just above. Notice that this measure, wavelength, then depends not only on the speed of propagation of the wave, but also on the period or frequency of the vibration. Not only do waves behave very differently from material objects in the context of transmission of momentum and energy, but they also interact with each other differently than material objects do.

When two objects meet each other they collide. Two waves, on the other hand, do not interact at all but pass "through" each other as ghosts pass through ghosts. But in the region where the two passing waves overlap the effective disturbance becomes a net sum of the disturbances of the two waves. So, when a floater happens to be "at the wrong place at the wrong time", i.

But were it lucky to be where the peak of one wave meets the valley of another wave of equal amplitude, then it would not move at all; as if there were no waves passing by. This addition of disturbance, which does not affect the original waves, is purely a wave phenomenon and is called interference. So, waves do not collide, they interfere. Exercise: to see how two waves interfere, work with the applet: Wave Interference Try changing the wavelength of the waves and their amplitudes.

One of the interesting results is when the two waves have the same amplitudes and almost the same wavelengths, but not quite. Another wave characteristic that has no analog when it comes to travel of material objects is that when a wave reaches an obstacle or an opening , with dimensions comparable to its wavelength, it bends around the obstacle and about the opening. This second wave phenomena is called the diffraction effect. Check the applet on Wave Diffraction to see how this works.

Try changing the opening size to see how the effects of diffraction sharpen up or get washed out. Questions on Waves. Electrically charged objects attract or repel each other, just as two magnets attract or repel each other. The electric force that acts between charges has significant differences from the magnetic force that results in the interaction of magnets.

But, for the topic at hand, these forces behave very much the same way in that they are both of the " action-at-a-distance " type. That is to say, these forces manifest themselves in the absence of any physical contact between the objects that interact with each other. For example, two magnets exert forces on each other even while they are apart and neither is touching the other. In fact, the reason that a compass works is that its small magnetized needle rotates because of the magnetic force of the earth, as if manipulated by a ghost.

Another way model of explaining this interaction is to state that the earth's magnetic core establishes a magnetic field everywhere in space. It is this field that affects the compass needle. This concept of "field" is useful because once we know the field of the earth, then we know how any magnet would be affected once it enters this field.

The field provides an intermediary to understand how action at a distance can work. With electric charges, each charge produces an electric field which then in turn interacts with other electric charges.

Another advantage of the field concept is that it allows for an easier visualization of what happens when one of the charges or magnets begins to move. In this view, when a charge changes position, the field that it produces also changes in space.

In fact, as the charge oscillates, so does its field. This oscillating field is what is called an electromagnetic wave. By making a charge oscillate at one point in space we can cause another charge located further away to undergo oscillatory motion. Similar to mechanical waves, such as sound and water waves, electromagnetic waves are characterized by their frequency, speed, and amplitude. The above picture shows how both the magnetic and electric fields oscillate as the wave propagates to the right.

One interesting aspect of an electromagnetic wave that sets it apart from all other waves we have examined so far is that its propagation requires no medium.

Water waves, which are transverse, of course need water to propagate in. Sound waves, which are longitudinal, also need a matter medium; although almost any type of matter would do for them sound travels in air, all known gases, in fluids, in solids, and in plasma, a gas of charged ions. But oscillating electromagnetic fields travel even in vacuum.

Another interesting feature of electromagnetic waves relates to their speed of propagation. Some examples of simple harmonic motion are the motion of a simple pendulum for small swings and a vibrating magnet in a uniform magnetic induction. Consider a particle performing an oscillation along the path QOR with O as the mean position and Q and R as its extreme positions on either side of O. Suppose that at a given instant of the oscillation, the particle is at P.

The displacement is always measured from the mean position, whatever may be the starting point. The frequency of oscillation definition is simply the number of oscillations performed by the particle in one second. Therefore, the number of oscillations in one second, i. The human ear is sensitive to frequencies lying between 20 Hz and 20, Hz, and frequencies in this range are called sonic or audible frequencies. The frequencies above the range of human hearing are called ultrasonic frequencies, while the frequencies which are below the audible range are called infrasonic frequencies.

Frequencies of radiowaves an oscillating electromagnetic wave are expressed in kilohertz or megahertz, while visible light has frequencies in the range of hundreds of terrahertz.

She is a science editor of research papers written by Chinese and Korean scientists. She is a science writer of educational content, meant for publication by American companies. She has a master's degree in analytical chemistry. She has been a freelancer for many companies in the US and China. How to Calculate Oscillation Frequency. The word period refers to the time for some event whether repetitive or not; but we shall be primarily interested in periodic motion, which is by definition repetitive.

A concept closely related to period is the frequency of an event. For example, if you get a paycheck twice a month, the frequency of payment is two per month and the period between checks is half a month. Frequency f is defined to be the number of events per unit time. For periodic motion, frequency is the number of oscillations per unit time. The relationship between frequency and period is. The SI unit for frequency is the cycle per second , which is defined to be a hertz Hz :.

A cycle is one complete oscillation. Note that a vibration can be a single or multiple event, whereas oscillations are usually repetitive for a significant number of cycles. We can use the formulas presented in this module to determine both the frequency based on known oscillations and the oscillation based on a known frequency. Both Parts 1 and 2 can be answered using the relationship between period and frequency.

In Part 1, the period T is given and we are asked to find frequency f. In Part 2, the frequency f is given and we are asked to find the period T. The frequency of sound found in Part 1 is much higher than the highest frequency that humans can hear and, therefore, is called ultrasound. Appropriate oscillations at this frequency generate ultrasound used for noninvasive medical diagnoses, such as observations of a fetus in the womb. Identify the known values:The time for one complete oscillation is the period T :.

The period found in Part 2 is the time per cycle, but this value is often quoted as simply the time in convenient units ms or milliseconds in this case. Identify an event in your life such as receiving a paycheck that occurs regularly.