CLASS 10TH DAY 1
INTRODUCTION
ACTIVITY: REFRACTION
1.Place a coin at the bottom of a bucket filled with water. With your eye to a side above water, try to pick up the coin in one go. Did you succeed in picking up the coin?.
2.Place a large shallow bowl on a Table and put a coin in it. Move away slowly from the bowl. Stop when the coin just disappears from your sight. Pour water gently into the bowl without disturbing the coin. Keep looking for the coin from your position. Does the coin becomes visible again from your position? How could this happen?
The coin becomes visible again on pouring water into the bowl. The coin appears slightly raised above its actual position due to refraction of Light!
FOR DOUBTS(REFER VIDEO)👉 👉
But why does this happen lets find out ?👇👇
Light does not travel in the same direction in all media. It appears that when traveling obliquely from one medium to another, the direction of propagation of light in the second medium changes. This phenomenon is known as refraction of light.
The ability of a medium to refract light is also expressed in terms of its optical density. Optical density has a definite connotation. It is not the same as mass density. We have been using the terms ‘rarer medium’ and ‘denser medium’ in this Chapter. It actually means ‘optically rarer medium’ and ‘optically denser medium’, respectively. When can we say that a medium is optically denser than the other? In comparing two media, the one with the larger refractive index is optically denser medium than the other. The other medium of lower refractive index is optically rarer. The speed of light is higher in a rarer medium than a denser medium. Thus, a ray of light traveling from a rarer medium to a denser medium slows down and bends towards the normal. When it travels from a denser medium to a rarer medium, it speeds up and bends away from the normal.
PRISM
Take a thick sheet of cardboard and make a small hole or narrow slit in its middle .Allow sunlight to fall on the narrow slit. This gives a narrow beam of white light. Now, take a glass prism and allow the light from the slit to fall on one of its faces. Turn the prism slowly until the light that comes out of it appears on a nearby screen.
What do you observe? You will find a beautiful band of colours.
Why does this happen?👇 👇
The prism has probably split the incident white light into a band of colours.
The various colours seen are Violet, Indigo, Blue, Green, Yellow, Orange and Red, as shown in. The acronym VIBGYOR will help you to remember the sequence of colours. The band of the coloured components of a light beam is called its spectrum. You might not be able to see all the colours separately. Yet something makes each colour distinct from the other.
The splitting of light into its component colours is called dispersion. You have seen that white light is dispersed into its seven-colour components by a prism. Why do we get these colors? Different colors of light bend through different angles with respect to the incident ray, as they pass through a prism. The red light bends the least while the violet the most. Thus the rays of each color emerge along different paths.
Dispersion of Light and Spectrum are discussed in this Colorful video! Is White Light really white in color? How is a Rainbow formed? These are discussed in the video along with exciting experiments on Light. We look at Dispersion of Light through a glass Prism and how the VIBGYOR Spectrum is formed.
HUMAN EYE
The human eye belongs to a general group of eyes found in nature called “camera-type eyes.” Just as a camera lens focuses light onto film, a structure in the eye called the cornea focuses light onto a light-sensitive membrane called the retina.
>>Why do we have two eyes for vision and not just one?
There are several advantages of our having two eyes instead of one. It gives a wider field of view. A human being has a horizontal field of view of about 150° with one eye and of about 180° with two eyes. The ability to detect faint objects is, of course, enhanced with two detectors instead of one. Some animals, usually prey animals, have their two eyes positioned on opposite sides of their heads to give the widest possible field of view. But our two eyes are positioned on the front of our heads, and it thus reduces our field of view in favor of what is called stereopsis. Shut one eye and the world looks flat – two-dimensional. Keep both eyes open and the world takes on the third dimension of depth. Because our eyes are separated by a few centimeters, each eye sees a slightly different image. Our brain combines the two images into one, using the extra information to tell us how close or far away things are.
DID YOU KNOW
EYE DONATION
Do you know that our eyes can live even after our death? By donating our eyes after we die, we can light the life of a blind person. About 35 million people in the developing world are blind and most of them can be cured. About 4.5 million people with corneal blindness can be cured through corneal transplantation of donated eyes. Out of these 4.5 million, 60% are children below the age of 12. So, if we have got the gift of vision, why not pass it on to somebody who does not have it? What do we have to keep in mind when eyes have to be donated?
Eye donors can belong to any age group or sex. People who use spectacles, or those operated for cataract, can still donate the eyes. People who are diabetic, have hypertension, asthma patients and those without communicable diseases can also donate eyes. Eyes must be removed within 4-6 hours after death. Inform the nearest eye bank Immediately. The eye bank team will remove the eyes at the home of the deceased or at a hospital. Eye removal takes only 10-15 minutes. It is a simple process and does not lead to any disfigurement. Persons who were infected with or died because of AIDS, Hepatitis B or C, rabies, acute leukaemia, tetanus, cholera, meningitis or encephalitis cannot donate eyes. An eye bank collects, evaluates and distributes the donated eyes. All eyes donated are evaluated using strict medical standards. Those donated eyes found unsuitable for transplantation are used for valuable research and medical education. The identities of both the donor and the recipient remain confidential. One pair of eyes gives vision to up to FOUR CORNEAL BLIND PEOPLE.
Fun Activity: Learn how to tie a tie in 8 ways through this video?
- Van Wijk knot
- Half Windsor knot
- Merovingian knot
- Trinity knot
- Full Windsor knot
- Eldredge knot
- Prince Albert knot
- Four In Hand knot
Analogy
Word Analogy means correspondence, in other words connection between two things or resemblance of one object to another in certain aspects.’
An analogy is a comparison in which an idea or a thing is compared to another thing that is quite different from it. It aims at explaining that idea or thing by comparing it to something that is familiar.
The questions on Analogy tests a candidate’s knowledge, power of reasoning.In these a particular relationship is given and another similar relationship has to be identified from the alternatives provided. There can be various kinds of relationship like instrument and measurement, part and whole, individual and group, worker and product.
TYPE 1 : COMPLETING THE ANALOGOUS PAIR
In this type of question, two related words are given. Another word is also given.The candidate is required to find out the relationship between the first two words and choose the word from the given alternatives, which has the same relationship to the third word, as the first two words have.
Ex. 1. Bombay : Maharashtra : : Trivandrum : ?
(a) Calcutta (b) Gujrat (c) Rajasthan (d) Kerala (e) Sikkim
Sol. This question is about state and its capital. Bombay is the capital of Maharashtra. Similarly, Trivandrum is the capital of Kerala. So, the answer is (d).
Ex. 2. Cattle : Herd :: Sheep : ?Â
(a) Flock (b) Swarm (c) Crowd (d) Shoal (e) MobÂ
Sol. This question is about group and individual. Herd is a group of cattle. Similarly, flock is a collection of sheep. So, the answer is (a).
TYPE 2 : SIMPLE ANALOGY
- Doctor is related to Patient in the same way as Lawyer is related to ?….. Â
(a) Customer (b) Accused (c) Magistrate (d) Client
Sol: Here first works for the second. Just like a doctor works for his patient, a lawyer works for his client.
- Needle is related to Thread in the same way as Pen is related to …..Â
(a) Ink (b) Cap (c) Paper (d) Word Â
Sol: Here second is inserted in the first. Just like a thread is inserted into a needle, ink is inserted in a pen.
TYPE 3 : CHOOSING THE ANALOGOUS PAIR
- Chalk : Blackboard
(a) Type : Paint (b) Table : Chair (c) Ink : Paper (d) Door : Handle
Sol . Just as chalk is used to write on a blackboard, so also ink is used to write on a paper. Hence, the answer is (c).
- Train : TrackÂ
(a)Idea : Brain (b) Water : Boat (c) Bullet : Barrel (d) Fame : Television
   Sol: A train moves on tracks. Similarly, a bullet travels through the barrel of the gun.
QUIZ TIME: Lets take a quiz to test your understanding.👇 👇
FUN ACTIVITY: Sixteen Soldiers
BOARD
An expanded Alquerque board is used. Two triangle boards are attached to two opposite sides of an Alquerque board. Each player has 16 pieces that are distinguishable from the other player. Pieces are placed on the intersections (or “points”) of the board, specifically on their half of the Alquerque board, and the nearest triangular board.
RULES
The following rules are based upon Parker’s description:
- Players alternate their turns
- A player may only use one of their pieces in a turn, and must either make a move or perform a capture but not both.
- A piece may move onto any vacant adjacent point along a line.
- A piece may capture an opposing piece by the short leap as in draughts or Alquerque. The piece must be adjacent to the opposing piece, and leap over it onto a vacant point immediately beyond. The leap must be in a straight line and follow the pattern on the board. Captures are not mandatory. A piece can continue to capture within the same turn, and may stop capturing any time. The captured piece (or pieces) is removed from the board.
- The player who captures all of the other player’s pieces wins.
If you need any help to understand the game follow the link below: