class 9-10

Antonie van Leeuwenhoek first discovered microbial life in the 1600s using a simple, single lens microscope that he made himself. This video gives instructions to build your own working Leeuwenhoek microscope, including the actual lens itself, using simple materials you likely have around the house.

The blind spot in our eyes is a tiny functional area about the size of a pinhead, where the optic nerve passes through the surface of the retina. This area has no photoreceptor cells that detect light, which creates the blind spot 

Two eyes give us a wider field of vision. It also helps us perceive the depth which forms a 3D impression and enhances the ability of assessing distinct position of object.

Binocular vision is a vision formed by using two eyes where there is an overlapping field of view.

When there is no water in the glass, the light from the coin experiences very little refraction and we can see the light from the penny. When there is water in the glass, the light from the coin experiences refraction (bending) and reflection (total internal reflection, TIR) such the light it is not able to reach the observer’s eyes. A small amount of refraction occurs as the light leaves the coin and travels through the bottom of the glass, then refraction occurs again as it enters the water. When refraction occurs at the side of the glass there is Total Internal Reflection because of the angle of incidence. The light ends up traveling at such an angle that we are unable to see the coin.

Total internal reflection is the phenomenon which occurs when the light rays travel from a more optically denser medium to a less optically denser medium.

When light passes from one medium to another, say air, a glass of water, then a part of the light is absorbed by particles of the medium, preceded by its subsequent radiation in a particular direction. This phenomenon is termed a scattering of light. The intensity of scattered light depends on the size of the particles and the wavelength of the light.

To measure the voltage, we simply need to select the DC function on our multimeter, and then we connect the red lead to the positive terminal and the black lead to the negative.

When a balloon is rubbed against a piece of wool or hair, it picks up electrons and becomes negatively charged. This negatively charged balloon can then attract neutral objects like paper. The negatively charged balloon attracts the neutrally charged paper by first repelling the negative charges away, which leaves the positive charges closer to the balloon. Since opposites attract, the paper is attracted to the balloon and is picked up.

When two straws are rubbed with a woolen cloth, they acquire the same kind of charge. The charges in the neutral straw get redistributed in such a way that opposite charges (opposite to the charge on the charged straw) come close to the charged straw. The attraction is caused by the attractive force between the induced charges and charges on the charged straw

Electrostatics is the study of electric charges at rest. It involves the forces between charges, the electric fields created by charges, and the resulting potential energy. Key concepts include Coulomb’s Law, which describes the force between two charges, and the concept of an electric field, a region around a charged particle where a force would be exerted on other charged particles. Electrostatic phenomena are evident in everyday life, from static electricity in clothing to the operation of electronic devices. 

Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field. Electric charge can be positive or negative.

Archimedes' principle states that the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially, is equal to the weight of the fluid that the body displaces.[1] Archimedes' principle is a law of physics fundamental to fluid mechanics.

Charles's law (also known as the law of volumes) is an experimental gas law that describes how gases tend to expand when heated. A modern statement of Charles's law is: When the pressure on a sample of a dry gas is held constant, the Kelvin temperature and the volume will be in direct proportion.

Boyle’s law is a gas law which states that the pressure exerted by a gas (of a given mass, kept at a constant temperature) is inversely proportional to the volume occupied by it.