polarity of water

19. Light in Water Light traveling in water of refractive index 1.33 is incident on a plate of glass with index of refraction 1.53. At what angle of incidence is the reflected light fully polarized?20. Completely Polarized (a) At what angle of incidence will the light reflected from water be completely polarized? (b) Does this angle depend on the wavelength of the light?

number pattern

Proper Fractions:              Fractions having numerator less than the denominator are called proper fractions.                   Example: `3/7, 7/13.`Improper Fractions:             Fractions having numerator that are larger than or equal to their denominators are called improper fractions.                   Example: `12/5, 6/6, 21/11.` Mixed Fractions:             Numbers having a whole number part and a fractional part are called mixed numbers. We denote a mixed number in the form a `b/c` .                   Example: `2 5/2, 1 1/3` . Decimal Fractions:            Fractions having denominator as 10, 100 or 1000 or any other higher power of 10 are called decimal fractions.                   Example: `4/100` ,` 35/1000.` Simple Fractions:          Fractions having both the numerator and denominator as whole numbers are called simple fractions.                   Example: 4/5, 6/95. Like and Unlike Fractions:            Fractions having the same denominators are called like fractions, whereas fractions having different denominators are called unlike fractions.                Example: `4/9, 1/9` are all like fractions.                               `3/5, 4/7` are all unlike fractions.

pressure definition

Introduction to vapour pressure mixture:Consider a mixture of liquids like water and alcohol in a container which is closed.The vapor presure exertedby each component is partial vapor presure of that component.First we would consider water vapor presure.

general knowledge facts

The zoogeography or the knowledge of the distribution of animals on the earth has led to the division of the world into a number of distinct zoogeographical (biogeo-graphical also) realms (Fig. 42.1). Originally these were based on the mammalian faunas of the various parts of the world, but their validity is general.

writing chemical formulas

    We have to find the equation of the line using the following formula`(y-y1)/(y2-y1)`=`(x-x1)/(x2-x1)`    Here (x1,y1) and (x2,y2) are the given two points.  Substitute the given points in the above formula we have to get the equation of the line.Example:(1, 3) and (4, 8) write the equation of the line that passing through the given two points by Method - 1Solution:Here x1 = 1 and y1=3 and x2=4 and y2=8The formula for equation of the line is `(y-y1)/(y2-y1)`=`(x-x1)/(x2-x1)`Substitute the x1, y1, x2 and y2 values in the above equation we have to get, `(y-3)/(8-3)`=`(x-1)/(4-1)`Simplifying this we can get, 3y=5x+4This is the equation of the line that passes through the given two points.

binomial formula

Q. 6. Explain Stefan's law of thermal radiation. (1996,2000,01,04)Ans. Stefan's Law : This law states that the radiant energy '£' emitted from the unit area of surface of a perfect black-body in unit time is proportional to the 4th powerof the absolute temperature of the body. -i.e. Â£ oc T4 or £ = oT4 _Where c is a constant which is called Stefan's constant and its value is 5 • 67 x 10~8 j/m2-s-K4.Suppose that a black-body having absolute temperature T\ is surrounded by a black enclosure at absolute temperature Tz- The body will emit a7|4 joule energy per second per unit area of its surface. At the same time it will absorb <rlf joule energy per second per unit area from the surrounding atmosphere. Thus net energy emitted by unit area of the body in unit time will be£1-£2=o(rl4-T24)The rate of emission of radiant energy from the area A of a body with emissive power e, at the absolute temperature T is given byE = oT4eAQ. 7. Establish Newton's law of cooling from Stefan's law. (1996,2000,01,04)Ans. Newton's Law of Cooling : This law states that if the temperature difference between a body and its surrounding is small then rate of cooling of the body (or rate of loss of heat by the body) is proportional to the temperature difference between the body and surroundings.i.e. rate of loss of heat « temperature differenceDerivation of Newton's Law From Stefan's Law: Suppose that a body is placed in air for cooling. Let the absolute temperature of the body and that of surroundings be Ti and T. Let e be the emissive power of the body. Then according to Stefan's law the net rate of loss of heat by the body is given by.A£ = ae(Ti4-T4)Let Ti-T + t wheret = 7} -T > 0is smallthen AE = ce[(T + t)i-T4]= aeT4 jl + 4—.......j -1 (Using Binomial Expansion)t < T, hence ^ is very small, hence higher degrees of ^ are neglected.= 4oeT3fv Atmosphere is very big as compared to the body, hence its temperature remains almost constant.Hence, rate of heat loss oc t (temperature difference)Q. 8. Draw spectral distribution curves of black-body radiation and write the effect of rise in temperature on it. (1996,2001)Or Draw the curves between energy and wavelength at different temperatures of a black-body radiations and write the conclusions drawn from these curves. (2003)Ans. Spectral Distribution of Black-Body Radiation : A perfect black-body, when heated upto high temperature, emits radiation of all possible wavelengths, that is why it is called full radiator. In 1899, two scientists Lummer and Pringsheim studied the spectral energy distribution in black-body radiation at differenl temperatures. They heated the black-body at differenl temperatures and at each temperature they plotted the radiant energy, emitted at different wavelengths againsl wavelength. The general shape of these curves are shown in the fig. 13 -2.Following conclusions were drawn from these graphs:(i) At a given temperature, the radiant energy 'E\ emitted by the black-body at wavelength 'A.' first increases with the wavelength and attains a maxima at a certain wavelength and then goes on decreasing.(ii) At a given temperature, maximum energy is emitted at a certain wavelength which is denoted by Xm.(iii) As the temperature is increased, the energy 'Ex emitted at wavelength X is also increased for each wavelength.(iv) The product of absolute temperature T of black-body and wavelength X,„ at which maximum energy is emitted, is a constant.i.e. XmT = b (constant)This law is called Wein's displacement law and the constant 'b' is called Wein's constant.From this law we can observe that, at low temperatures the maximum energy is emitted at larger wavelengths, but as the temperature is increased more energy is emitted in shorter wavelengths and maximum energy peak is shifted towards shorter wavelengths (see graphs).(iv) The area under these curves increases with increasing temperature directly as the 4th power of the absolute temperature of the body. That means the total radiant energy (measured by the area under the curve) emitted by the body is directly proportional to 4th power of the absolute temperature.i.e. ExT4Thus Stefan's law is also verified by these curves.Q. 9. Explain Planck's hypothesis of radiation. Discuss its importance in modern physics. (1997,98,99)Or State Planck's hypothesis. (2004)Ans. Planck's Hypothesis: According to this hypothesis, emission or absorption of radiant energy is not continuous process but is takes place in the form of small packets of energy. Each such packet is called a photon or quanta. The energy associated with a photon of radiation having frequency v is hv. Here 'h' is a constant called Planck's constant. Thus we can conclude that energies emitted by a body can be hv, 2hv,3hv....(integer multiple of hv) but not in between.Classical mechanics and thermo-dynamics could not explain the spectral energy distribution in black-body radiation. Planck, used his hypothesis and derive a formula to explain the spectral energy distribution in black-body radiation and found it in close agreement with the results of Lummer and Pringsheim experiments. Further Einstein successfully explained photo-electric effect on the basis of Planck's hypothesis. In this way Planck's hypothesis gained recogni tion.Q. 10. Find the expression for kinetic mass and momentum of photon using Planck's hypothesis. (1999,2004)Ans. Momentum of Photon: According to Planck's hypothesis, the rest mass mo of photon is zero and each photon travels with the speed of light c.If v is the frequency of photon, then its energy will be E = hv. Further if m is the kinetic mass of photon then by mass energy relation, we haveE = mc2.2 ' hv h f v 1)E = hv = mc => m = = — '•' ~ = -c2 cX V c X):. Kinetic mass of photon m = ~= —v c2cXIf p is the linear momentum of photon, thenp = kinetic mass x velocityor p=mc or p = (v velocity = c)h hvor p = — = —c/v c (â– -• X = c/v)Momentum p = — = —y X c

in situ conservation

In situ conservation is the most appropriate method to maintain species of wild animals and plants in their natural habiats. This approach in-cludes protection of total ecosystems through a network of protected areasThe common natural habitats (protectedareas) that have been set for in situ conservation ofwild animals and plants include —1. National parks2. Wildlife sanctuaries3. Biosphere reserves4. Several wetlands, tnangrooves and coralreefs.5. Sacred grooves and Lakes.In situ conservation ilso includes the intro-duction of plants and ani mal species back intoagricultural, horticultural and animal husbandrypractices so that they are cultivated/reproduced fortheir reuse by the farmers/animal husbandrypeople. Farmers and horticulturists have beentraditionally maintaining large genetic diversity ofcrop plants/flowers by savir g seeds for next plant-ing season by a wide variety of indegenously developed practices. For example, tubers,rhizomes, bulbs and seeds of large variety of plant species ai e stored by the far ners/horticulturists fortheir cultivation in the next sieason. Similarly, native species of cattle, which are better adapted to dis-eases, drought and other adverse conditions, arebeing maintained by animal husbandry people.