What is Simple Harmonic Motion?

1. Oscillation of a loaded spring
2. Vibrations of a tuning fork
3. Vibrations of the balance wheel of a watch
4. A freely suspended magnet in a uniform magnetic field oscillates in a simple harmonic motion.

Important Features of Simple Harmonic Motion

1. The motion of the particle is periodic
2. It is the oscillatory motion of the simplest kind in which the particle oscillates back and forth above its mean position with constant amplitude and fixed frequency.
3. Restoring force acting on the particle is proportional to its displacement from the mean position.
4. The force acting on the particle always opposes the increase in its displacement
5. A simple harmonic motion can always be expressed in terms of a single harmonic function of sine or cosine.

Important Terms Related to Simple Harmonic Motion

1. Harmonic Oscillator: a particle executing simple harmonic motion is called a harmonic oscillator.
2. Displacement: the distance of the oscillating particle from its mean position at any instant is called its displacement. It is denoted by x.
3. Amplitude: the maximum displacement of the oscillating particle on either side of its mean is called its amplitude.
4. Oscillation: one complete back and forth motion of a particle starting and ending at the same point is called a cycle or oscillation
5. Time period: the time taken by a particle to complete one oscillation is called a time period.
6. Frequency: it is defined as the number of oscillations completed per unit time by a particle.
7. Angular Frequency: it is the quantity obtained by multiplying frequency by a factor of 2ℼ
8. Phase: the phase of a vibrating particle at any instant gives the state of the particle as regards its position and the direction of motion at that instant. Suppose a simple harmonic equation is represented by:

Summarized Notes On Simple Harmonic Motion

1. A particle is said to execute simple harmonic motion if it moves to and fro about a mean position under the action of a restoring force which is directly proportional to its displacement from the mean position.
2. For a simple harmonic motion, acceleration is directly proportional to the displacement
3. The equation of SHM can be given by: x = Acos(ɷt + 𝚹)
4. 
   

Gold Foil Experiment

1. A large portion of the alpha beam passed through gold foil without getting deflected. This suggests that a major portion of the atom is empty.
2. Just a fraction of alpha particles were deflected during this experiment suggesting that positive charge is not evenly distributed in the atom as assumed in the Plum Pudding model. But rather, it is concentrated over a very small area.
3. The third observation made was that only very few alpha particle rays were deflected back at 180°. That means the volume of positive charge occupied in the atom is very small in comparison to the total volume of the atom itself.

Postulates of Rutherford Model of Atom

1. Atom is composed of negatively and positively charged particles called electrons and protons. The majority of the mass is concentrated at the center of the atom known as the nucleus.
2. Electrons revolve around the nucleus at a very high speed in a fixed path known as orbits.
3. Atoms are electrically neutral and the electrostatic attraction holds the electrons and protons together
4. The volume occupied by the nucleus is very small in comparison to the volume occupied by atom.

Drawbacks of Rutherford Model of the Atom

1. However, this never happens. Thus, the Rutherford model of atom failed to explain the Stability of atom. 
2. The Rutherford model of the atom also failed to explain the structure of atoms.
3. Furthermore, the model also failed to explain the existence of certain definite lines in the hydrogen spectrum. If the electrons were to lose energy continuously, the atomic spectrum of hydrogen should have been continuous. However, the spectrum of hydrogen is found to be discontinuous in the form of characteristics lines of definite wavelengths.

Summarized Notes On Rutherford Model Of Atom

1. J.J Thomson discovered electrons. He also proposed the plum pudding model.
2. Ernest Rutherford discovered protons and through his Gold foil experiment proposed a new model of the atom.
3. The new model of the atom that Ruderford proposed resembles the solar system.
4. Most of the volume in an atom is empty.

We usually talk about vitamins but do we know what are vitamins? The vitamins are important as they perform various functions in the body. The deficiency of vitamins may take place as the food which you intake might not have enough of vitamin contents. This deficiency of vitamins hampers proper body functioning. To have a balanced diet enriched with the vitamins we need to know about the vitamins, their importance and sources. Read this article to know about different Vitamins and their sources and their importance.

Vitamins and Their Sources

There are 13 essential vitamins that are important for a human body. These vitamins are divided into two categories, fat-soluble and water-soluble vitamins. Given below in the table are the Different vitamins and their sources.

Fat-Soluble Vitamins	Water-Soluble Vitamins
It is stored in the body’s fatty tissue.	It is not stored in the body.
Fat-soluble vitamins are – A,D,E, K	Water-soluble vitamins are – B1, B2, B3, B5, B6, B7, B9, B12, Vitamin C

Vitamins and Their Sources: What are Fat-Soluble Vitamins

The fat-soluble vitamins are similar to oil and do not dissolve in water. Fat-soluble vitamins are most abundant in high-fat foods and are much better absorbed into your bloodstream when you eat them with fat. Given below is the table with the list of different vitamins and their sources from which you can get, their importance for the body.

Vitamins	Importance	Sources
Vitamin A	This vitamin is vital for vision. This vitamin provides healthy skin and mucous membranes. It also improves bone and tooth growth. It is vital for improving immunity.	Fortified milk Cheese Cream Butter fortified margarine Eggs  Liver Leafy vegetables Apricots  Carrots Sweet potatoes Pumpkin.
Vitamin D	It is essential in proper absorption of calcium stored in bones.	Egg yolks Liver Fatty fish Fortified milk Fortified margarine Sunlight.
Vitamin E	It protects cell walls.	Soyabean, corn e.t.c. Leafy green vegetables Wheat germ Whole-grain products Liver Egg yolks Nuts and seeds.
Vitamin K	It essential for proper blood clotting.	Kale Collard greens Spinach Broccoli Brussels sprouts Asparagus Produced in the intestinal tract by bacterias.

Vitamins and Their Sources: What are Water-Soluble Vitamins

Water-Soluble Vitamins are vitamins that can dissolve in water. These vitamins are carried to the body’s tissues but are not stored in the body. They are found in animal foods and plants or dietary supplements and should be taken daily. Both Vitamin C and members of the vitamin B complex are water-soluble. To know more about Water-Soluble Vitamins and their Sources, refer to the table given below.

Vitamins	Importance	Sources
Thiamine (vitamin B1)	The part of an enzyme which is required for energy metabolism. It is significant in nerve functioning.	Pork Whole-grain Enriched breads Cereals Legumes Nuts and seeds. It is found in all nutritious food in moderate amounts.
Riboflavin(vitamin B2)	The part of an enzyme is needed for energy metabolism. It is important for normal vision & skin health.	Milk and milk products Leafy green vegetables Whole-grain Enriched  breads Cereals.
Niacin (vitamin B3)	This vitamin helps in maintaining: healthy skin nerves digestive system.	Meat Fish Whole-grain Enriched breads Cereals Mushrooms Leafy green vegetables Peanut butter.
Pantothenic acid	This vitamin is essential for the metabolism of food.	It is widespread in almost all food.
Biotin	Important in metabolism of proteins and carbohydrates. It also helps in the production of hormones and cholesterol.	It is widespread in food. It is produced in the intestinal tract by bacteria.
Pyridoxine (vitamin B6)	The part of an enzyme needed for protein metabolism. It helps in making red blood cells.	Meat Fish Poultry Vegetables Fruits.
Folic acid	The part of an enzyme is needed for making DNA. This also required for new cells i.e. red blood cells.	Leafy green vegetables Legumes Orange juice Liver It is now added to most refined grains.
Cobalamin (vitamin B12)	The part of an enzyme needed for making new cells. It is important for nerve functioning.	Meat Poultry Fish Seafood Eggs Milk and milk products It is not found in plant foods.
Ascorbic acid (vitamin C)	This promotes healthy teeth & gums. It is needed for healthy immune system. The part of an enzyme is needed for protein metabolism. It helps in iron absorption.	Citrus fruits Cabbage family Cantaloupe Strawberries Peppers Tomatoes Potatoes Lettuce Papayas Mangoes Kiwifruit.

Hope this article on vitamins and their sources was informative and helpful in your exam preparation. If you have any queries related to the article, do mention in the comments section.

If the light rays pass from one medium to another, at the boundary of two mediums, they shift their path. Refraction is a wave’s bending when it enters a medium at different speeds.

What is the Refraction of Light?

Refraction is a shift in the path of a wave that travels from one medium to another or a gradual change in the medium. Light refraction is one of the most commonly observed phenomena which involves light refraction by a prism. We all understand that in different mediums the speed of light is variable. It happens because of the change in the speed of light from one medium to another.

Refraction of Light

It is called refraction of light when the light rays either bend or change their direction while passing from one medium to the other. When light travels from air to glass, from glass to air, from air to water or from water to air, light refracts.

Laws of refraction states that: the ray of the incident, the refracted ray, and the normal at the point of incidence to the interface of two mediums are all on the same plane.

Important Terms

• The incident ray is considered as an event when the light rays travel from air into glass or liquid.
• The point of incidence is called normal.
• The angle between the incident ray and the normal is the Angle of Incidence.
• The angle between the refracted ray and the normal is the angle of refraction.
• The refraction angle is either smaller or larger than the incidence angle.

Causes of Refraction

The reason for light refraction is as follows

1. the refracted ray amplitude remains constant.
2. The frequency of the refracted ray will be smaller than the incident ray owing to partial reflection and absorption of light at the interface.
3. When the light reaches the border of two different media, light divergence happens due to refraction, resulting in a shift of wavelength and light frequency.

Q.1 What is an optically rarer medium and optically denser medium?

The optically rarer medium is when the speed of light is greater. Whereas, the optically denser medium is when the speed of light is less

For e.g. Glass is a medium that is optically denser than water and air.

As light rays pass from a rarer optical medium to a denser medium, it bends towards the normal. The angle of refraction in this situation is greater than the angle of incidence. It bends as normal as light rays pass from air into glass or air into liquid. This is because, while traveling from air to glass or water, the speed of light rays declines.

As light rays travel from a more optically dense medium towards a more rare medium, it bends away from the normal. In this situation, the refraction rate is greater than the incidence angle. It bends away from the normal as light rays travel from glass to air or from liquid to air.

Q.2. What if the refraction of light takes place twice in case?

For example, when it exits from the air into the glass slab and the other when it enters the air through the glass slab.

As light rays enter the glass slab passing through air it becomes refracted and bend toward the normal. Then, when it falls out of the glass slab the path of the refracted ray shifts again. In this scenario, the rays of the incident and the emerging rays are similar. The perpendicular distance between the incident ray’s original path and the emergent ray from the glass slab is called the lateral displacement of the emergent ray of light and the angle that the emerging ray makes with the normal is called the emergence angle.

Reflection of Light Types

Specular or Regular Reflection

Diffuse or Irregular Reflection

How do we see things?

1. Focusing image on retina
2. Refraction of light

Summarized Notes On Reflection Of Light

1. When a light ray falls on an interface and returns back to travel in the same medium then it is known as a reflection of light.
2. Specular and diffuse are two types of reflection. Specular reflection occurs through polished surfaces while diffuse reflection occurs through rough surfaces
3. Diffuse reflection is the reason for our visibility.
4. The objects which do not reflect light are not visible.

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