## Wave

It is a disturbance produced in a medium which passes through the medium without changing its shape and size.

### Types of Wave

There are 2 types of waves:
1. Mechanical waves: These require a medium for propagation. These waves can not travel in the absence if medium. Eg: Sound Wave
2. Non-mechanical Waves. These waves do not require any medium for propagation.These waves can also travel in vacuum and space. Eg: Radio Waves

### Types of Mechanical Waves

#### Transverse Waves

• In transverse waves, particle vibrates perpendicular to the direction of the wave.
• Transverse waves travel in form of crest and trough.
• Transverse waves can propagate only in solid mediums and only on the surface of liquid.
• They can not travel inside a liquid on inside a gaseous medium.

#### Longitudinal Waves

• In Longitudinal Waves, particles vibrate along the direction of propagation of the wave.
• Longitudinal Waves travel in the form of compression and rarefaction.
• The density and pressure of the medium are maximum at the compression as the particles come closer to each other and minimum at the rarefaction as the particles move away from each other.
• Longitudinal Waves can be produced in all the 3 mediums.

### Characteristics of a Wave

#### Amplitude

Amplitude is the maximum displacement of the vibrating particle from the mean position. It is denoted by 'a'.

#### Time Period

The time period is the time taken to complete one vibration/ oscillation or time taken to complete 2 consecutive compressions or 2 consecutive rarefactions. It is denoted by 't' and its SI unit is second.

#### Frequency

Frequency is the number of vibrations or oscillations in one second. It is denoted by 'nuu'. Its SI unit is Hertz or Hz

#### Wave Length

Wavelength is the distance between 2 consecutive compressions and rarefaction. It is denoted by Î» (lambda) and its SI unit is metres.

### Anode Ray Experiment

→Anode ray experiment was conducted by E Goldstein. →These rays are also known as canal rays. →This experiment helped in the discovery of the proton. Apparatus Used A discharge tube  was taken in which there were 2 electrodes i.e. Anode(+ve) and the cathode (-ve). The tube was filled with an inert gas. A perforated or porous cathode was used. A layer of zinc sulphide was placed at the back of the cathode. There was a vacuum pump in the tube. High voltage (5000v-10000v) was allowed to flow through the system. It was observed that when the gas was at 1atm(atmospheric pressure ) no change was seen in the tube.  When the   pressure   was decreased inside the tube, a glow could be seen at the back side of the cathode.

### Levitation 2

LEVITATION II To be completely honest I was going to start this with a pun. I did think of one but it doesn’t float… I am sorry I just had to. Anyway, this is the second part to the article on super cool ways of making things levitate. Go check the first part out if you haven’t already. Actually, the first part may have become repulsive with all the magnets and stuff, but I promise this will be more attractive. Get it? No? I’ll stop now. I am just going to jump straight into it. 1.    Electrostatic Levitation I know you are probably sick and tired of magnets but they are the best way you know… This method is somewhat similar. You remember that cool science experiment you did with two straws attracting or repulsing each other based on their charge? So basically using the same principle we can make a charged object levitate. But before you try it, let me tell you it won’t be easy. Even impossible according to our Mr. Earnshaw. He even made a law (the law is

### Animal and Plant Cells

Cells Cells are the basic functional, biological and structural unit of life. The word cell is a Latin word meaning ‘small room’. Cells are also known as building blocks of life.  The branch of science that deals with the form, structure, and composition of a cell is known as Cytology. All organisms around us are made up of cells. Bacteria, ameba, paramecium, algae, fungi, plants and animals are made up of cells.  Cells together form tissues. And tissue together makes an organ. History Of Cell The cell was discovered by Robert Hooke in 1665. He assembled a simple microscope and observed a very thin slice of cork under his primitive microscope. The cork was obtained from the outer covering of a tree called bark. Robert Hooke observed many little-partitioned boxes or compartments in the cork slice. These boxes appeared like a honey-comb. He termed these boxes as the cell. He also noticed that one box was separated from another by a wall. What Ho

### Isotopes, Isobars and Isotones

Isotopes These are elements which have the same atomic number but different atomic mass . They have the same atomic number because the number of protons that are inside their nuclei remains the same. But, they have different atomic mass because the number of neutrons that are also inside their nuclei is different. As the number of protons inside nuclei remains same, therefore the overall charge of the elements also remains same as in isotopes: no of protons = no of electrons . Hence, as isotopes overall charge remains neutral, therefore their chemical properties will also remain identical.   Therefore, Isotopes are chemically same but physically different.