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3551.

A ray of light strikes a glass slab 5 cm thick, making an angle of incidence equal to 30^(@). (a) Draw a ray diagram showing the emergent ray and the refracted ray through the glass block. The refractive index of glass is 1*5. (b) Measure the lateral displacement of the ray. The sin 19*5^(@)=1//3.

Answer»

SOLUTION :(a) : `mu=1*5,i=30^(@)`
Let us FIRST calculate the angle of refraction R.
From Snell.s law, `(SINI)/(sinr)=mu`
`therefore sinr=(sini)/(mu)=(sin30^(@))/(1*5)=(1//2)/(1*5)=(1)/(3)`
or `r=19*5^(@)` (since `sin19*5^(@)=1//3`)
The ray diagram is given in FIGURE. the refracted ray is drawn with angle of refraction `19*5^(@)` and emergent ray is drawn parallel to the incident ray.

(b) Lateral displacement=1 cm nearly (on proper scale).
Discussion
3552.

Establish a relationship to determine the equivalent resistance R of a combination of three resistors having resistances R_(1), R_(2) and R_(3) connected In series. Calculate the equivalent resistance of the combination of three resistors of 2 Omega, 3 Omega and 6Omega joined in parallel.

Answer»

Solution :An applied potential V PRODUCES current I in the resistors `R_(1),R_(2)`and `R_(3)`, causing a potential drop `V_(1)V_(2)` and `V_(3)` respectively through each resistor.

Total Potential `, V = V_(1) +V_(2) +V_(3)`
By Ohm.s Law `V_(1) =IR_(1)`
`V_(2)= IR_(2)`
`V_(3)=IR_(3)`
THUS `V=IR_(1)+IR_(2)+IR_(3)`
`=I(R_(1)+R_(2)+R_(3))`
IF R is the equivalent resistance `V=IR `
Hence `IR = I(R_(1)+R_(2)+R_(3))`
`R=R_(1)+R_(2)+R_(3)`
This proves that overall resistance increases when resistors are connected in series. Three resistors `2 OMEGA, 3 Omega`and `Omega`, are joined in parallel combination.
Equivalent resistance
`(1)/(R_(p))=(1)/(2)+(1)/(3)+(1)/(6)`
`= (2+2+1)/(6) =(6)/(6)`
`R_(p)= 1Omega`
Discussion
3553.

Redraw the circuit of question 1, putting in an ammeter to measure the current through the resistors and a voltmeter to measure potential difference across the 12 Omega resistor. What would be the readings in the ammeter and the voltmeter?

Answer»

Solution :
`R_(s) =(5+8+12)`
`=25 Omega`
V= IR
`I = (V)/(R) = (6)/(25) = 0.24 A `
Potential DIFFERENCE across `12 Omega` resistor is
`V = IR = 0.24xx12= 2.88` V
HENCE reading of AMMETER `= 0.24 A` reading of voltmeter = 2.88 V
Discussion
3554.

Define power.

Answer»

<P>

SOLUTION :(i) Ability of a LENS to converge (convex lens) or diverge (concave lens) is called as its power.
(ii) The power of a lens can be defined as the degree of convergence or divergence of light rays.
(iii) Power of a lens is numerically defined as the reciprocal of its focal length .
`P=(1)/(f)`
The SI unit of power of a lens is dioptre.
Discussion
3555.

List two precautions to be taken to avoid overloading in the domestic circuit. Also state one difference between overloading and short circuiting.

Answer»

SOLUTION :Precautions :
(i) A fuse of APPROPRIATE rating should be USED in the circuit.
(ii) Too many appliances should NEVER be connected to a single socket.
Overloading : Occurs when a large number of higher current drawing appliances are switched on at the same TIME and the total current drawn
through the circuit exceeds its rated value.
Short circuiting : Occurs when the live wire comes in direct contact with neutral wire.
Discussion
3556.

Out of two element A and B with mass number 2 and 235 respectively, Which one is suitable for making a) A nuclear reactor b) A hydrogen bomb Name the nuclear reaction involved in each case, write one difference between the two types of nuclear reactions.

Answer»

Solution :a) For a NUCLEAR reactor-element .B. with mass number 235 is suitable as a FUEL in a nuclear reactor.
b) For a hydrogen boomb- element ‘A’with mass number 2 is suitable for making the hydrogen bomb.
The nuclear reaction involved in
a) Nuclear reactor is nuclear fission reaction
b) Nuclear bomb is nuclear fusion reaction.
Difference between fission and fusion:
Fusion reaction releases much greater energy with NON radioactive products than the energy released in fission reaction with radio-active products.
Discussion
3557.

In C.G.S. system, the unit of linear momentum is kg ms^(-1).

Answer»


Solution :Correct STATEMENT : In C.G.S. SYSTEM, the unit of linear MOMENTUM is `g cms^(-1)`.
Discussion
3558.

Which of the following is not an example of a bio- mass energy source ?

Answer»

WOOD
GOBAR Gas
NUCLEAR ENERGY
Coal

Solution :Nuclear energy
Discussion
3559.

Which of the following can be produced during the nuclear fission as well as nuclear fusion reactions ?

Answer»

PROTONS
deutrons
electrons
neutrons

Answer :D
Discussion
3560.

Define gravitational potential energy and derive an expression for it associated with two particles of masses m_1" and "m_2.

Answer»

Solution :Gravitational potential energy of a body at a point in a gravitational FIELD of another. It is defined as the amount of work done in brining the given body from infinity to that point in the field is called Gravitational potential energy.
Expression for gravitational potential energy : CONSIDER two PARTICLES of masses `m_1" and "m_2` are placed at the POINTS 'O' and p respectively. Let the distance between the two particles is 'r' i.e.,OP=r.

Let us calculate the gravitational potential energy of the particle of mass `m_2` placed at point p in the gravitational filed of `m_1`. Join OP and extended it in forward direction. Consider two points A and B on this line such that OA= x and AB=dx.
The gravitational force of attraction on the prticle at A, `F=(Gm_1m_2)/(x^2)`
Small amount of work done in bringing the particle without accletation through a very small distance AB is, dW=Fdx `=(Gm_1m_2)/(x^2)dx`.
Total workdone in bringing the particle from infinity to the point P is,
`W=int_(oo)^(r )(Gm_1m_2)/(x^2)dx=Gm_1m_2 int_(oo)^(r )x^(-2)dx`
`= -Gm_1m_2[(1)/(x)]_(oo)^(r )= -Gm_1m_2[(1)/(r )-(1)/(oo)] =(-Gm_1m_2)/(r )`.
Since, this work done is stored in the particle its gravatational potential energy. Therefore, gravitational potential energy of the particle of mass `m_2` placed at point 'p' in the gravitationl field of particle of mass `m_1` at distance r is, `U=(-Gm_1m_2)/(r )`
Here, negetive sign shows that the potential energy is due to ATTRACTIVE gravitational force between two particles.
Discussion
3561.

Nichrome is an alloy of ___________ and Chromium.

Answer»


ANSWER :NICKEL, CHROMIUM
Discussion
3562.

__________ serves as a reference point to measure the electric potential.

Answer»

SOLUTION :GROUND CONNECTION
Discussion
3563.

(b) How can biodiversity be conserved ?

Answer»

Solution :Biodiversity can be conserved by the following ways :
(1) Protecting of the rare species of plants and animals
(2) Creating habitats for the animals and plants by establishing National Parks and Sanctuaries .
(3) Declaration of bioreserves , the areas which are protected through conservation. (4) Conservation projects for protecting special species .
(5) Conservation of all flora and fauna .
(6) STRICT observance of the acts and rules .
(7) Use of TRADITIONAL knowledge and MAINTAINING record of traditional knowledge.
Discussion
3564.

What is the work done by the electric force on uint charge ?

Answer»

SOLUTION :Work done by the electric force on uint CHARGE `V=(W)/(q)=(E_(e)L)/(q).` It is CALLED potential difference.
Discussion
3565.

Strong heating of ferrous sulphate leads to the formation of a brown solid and two gases. This reaction can be categorised as

Answer»

DISPLACEMENT and REDOX.
decomposition and redox.
displacement and endothermic.
decomposition and exothermic.

Solution :It is decomposition as WELL as redox. FERROUS is oxidised to FERRIC
Discussion
3566.

A 2.0 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 10 cm. The distance of the object from the lens is 15 cm. Find the nature, position and size of the image. Also find its magnification.

Answer»

Solution :It is GIVEN that Object-size h = +2.0 cm, FOCAL LENGTH f = +10 cm, Object-distance u = - 15 cm.
USING lens formula, we have
`(1)/(v) = (1)/(u) + (1)/(f) = (1)/((-15)) + (1)/(10) = - (1)/(15) + (1)/(10) = (-2 + 3)/(30) = + (1)/(30)`
or v = + 30 cm
The positive sign of v shows that the image is formed at a distance of 30 cm to the other side of the optical CENTRE of the lens and is a real and inverted image.
Magnification, `m = (h.)/(h) = (v)/(u) = (+ 30 cm)/(-15 cm) = -2`
Image-size, h. = (+2.0) 9+30/-15) = - 4.0 cm
Discussion
3567.

Fill in the blanks: Q: Critical angle is the angle of ____in denser medium for which the angle of ____in rarer medium is ____-

Answer»


ANSWER :INCIDENCE, REFRACTION, `90^(@)`.
Discussion
3568.

The weight of a body is ………………………… at the poles than at the equatorial region.

Answer»

More
less
zero
one

Solution :more
Discussion
3569.

Define the power of lens. The power of lens is +2.0 D. (i) Find the focal of lens in m. (ii) Name the kind of this lens. Explain with the help of figure whether this lens would converge or divere a beam of lens.

Answer»

Solution :(i) The ability of a LENS to converge/ diverge a BEAM of LIGHT rays is expressed in terms of its power (P), It is the inverse of focal LENGTH F (in meters).
Hence power of a lens is given by the relation
`P=1/(f("in meters"))`
`F=1/P=+1//2=+0.5m`
(ii) Convex lens
Discussion
3570.

what is salting out of soap:

Answer»

Solution :Manufacture of soap:KETTLE PROCESS:
This is the oldest method. But, it is still widely used in the small scale preparation of so There are mainly, TWO steps to be followed in this process.
(i) Saponification of oil:The oil, which is used in this process, is TAKEN in an iron tank (kettle). The alkaline solutia (10%) is added into the kettle, a LITTLE in excess. The mixture is boiled by passing steam through it. The oil gets hydrolysed after several hours of boiling. This process is called Saponification.
(ii) Salting out of soap:COMMON salt is then added to the boiling mixture. Soap is finally precipitated in the tank After several hours the soap rises to the top of the LIQUID as a .curdy mass.. The neat soap is taken off from the top. It is then allowed to cool down.
Discussion
3571.

Do you know the reasons for appearance the red colour of sun during sunrise and at sunset ?

Answer»

Solution :The light rays from the sun TRAVEL more distance in atmosphere to reacah our eye in morning and evening times. During SUNRISE and sunset EXCEPT red colour all colours scatter more and vanish before they reach us . Since scattering of red light is very less. It reaches us . As a RESULT sun APPEARS sun appears reddish during sunrise and sunset.
Discussion
3572.

What type of chemical reactions take place when electricity is passed through water ?

Answer»

DISPLACEMENT
Combination
DECOMPOSITION
Double displacement

Solution :Decomposition
Discussion
3573.

Quantisation of charge implies

Answer»

CHARGE does not exiet
charge EXISTS on particles.
there is a minimum permissible magnitude of charge
charge can't be created.

SOLUTION : there is a minimum permissible magnitude of charge
Discussion
3574.

Assertion (A): When white light passes through a tiangular prism, the emergent light consists of light of seven colours. Reason (R):Name of seven colours can be remembered by the acronym VIBGYOR.

Answer»

Both (A) and (R) are TRUE and (R) is CORRECT explanation of the assertion.
Both (A) and (R) are true but (R) is not the correct explaration of the assertion.
(4) is true but (R) is FALSE.
(A) is false but (R) is true.

Solution :While passing through a triangular prism WHITE light is splitted up into seven colours on account of the dispersion of light.
Discussion
3575.

The rise of sea-water during high tide is caused by the gravitational pull of the :

Answer»

SUN
Earth
Moon
Mars

Answer :C
Discussion
3576.

Rabbit do not have _________ teeth.

Answer»

INCISORS
canine
premolar
molar

Answer :B
Discussion
3577.

At what temperature is the rms velocity of a hydrogen molecule equal to that of an oxygen molecule at 47^(@)C?

Answer»

`-73K`
`3K`
`20K`
`80K`

SOLUTION :`v_(1)=SQRT((3RT_(1))/(M_(1)))`, `v_(2)=sqrt((3RT_(2))/(M_(2)))` i.e. `T_(1)=(M_(1))/(M_(2))T_(2)=(2)/(32)xx320=20K`
Discussion
3578.

Critical velocity depends on mass.

Answer»

SOLUTION :False - CRITICAL VELOCITY does not DEPEND on mass.
Discussion
3579.

Give reasons Circulation of blood in aquatic vertebrates differs from that in terrestrial vertebrates.

Answer»

Solution :Aquatic vertebrates take in oxygen DISSOLVED in water through gills which is then ABSORBED into their blood while TERRESTRIAL animals EXCHANGE these gases (`O_(2)` and `CO_(2)` ) in lungs.
Discussion
3580.

Artificial satellites use ………. as the main source of energy.

Answer»

SOLUTION :SOLAR CELL.
Discussion
3581.

Interatomic space in increasing order ______,___________ and__________.

Answer»

SOLUTION :SOLID, LIQUID, GAS
Discussion
3582.

Covalent compounds have low melting and boiling point. Why?

Answer»

SOLUTION :Intermolecular FORCES of ATTRACTION between the MOLECULES are WEAK.
Discussion
3583.

Define angle of incidence and angle of refraction.

Answer»

Solution :ANGLE of incidence is the angle i made by the INCIDENT ray with the NORMAL. Angle of refractive is the angle r made by the REFRACTED ray in the second medium with the normal.
Discussion
3584.

Concentrated hydrochloric acid reats more vigorously with calcium carbonatethan dilute hydrochoric acid.

Answer»

Solution :(1) The rate of a reaction INCREASES with the concentration of the reactant.
(2) As concentrated HYDROCHLORIC acid contains more number of HCl molecules than those in an equal VOLUME of dilute HCl, concentrated HCl reacts more vigorously with calcium CARBONATE.
Discussion
3585.

The rays of light travelling through the optical centre of a lens pass without changing their path. Is it true? justify

Answer»

Solution :The PORTION of a lens near the optical centre is LIKE a very thin SLAB of glass. Hence , the RAYS of LIGHT travelling through the optical centre of a lens pass wihtout changing their path.
Discussion
3586.

Which unit is a measure of an individual's exposure to gamma radiation ?

Answer»

SOLUTION :ROENTGEN
Discussion
3587.

Match II {:("1. Fuel", "(a) lead"), ("2. Moderator", "(b) Heavy water"), (3. "coolant", "(c) Graphit"),(4. "Shield" , "(d)uranium"):}

Answer»

Solution :1 (d) URANIUM 2. (C) Graphite, (3)heavy water4.(a) LEAD
Discussion
3588.

The door of a running refrigerator inside a room is left open. The correct statement out of the following ones is

Answer»

The room will be COOLED slightly
The room will be warmed up gradually
The room will be cooled to the temperature inside the refrigerator
The temperature of the room will remain unaffected.

Solution :C.O.P `=Q_2/W=T_2/(T_1-T_2)`
when DOOR is left open `T_2 rarr T_1` , HENCE C.O.P. `UARR`i.e. `theta_2uarr` . So HEAT energy given to the room increases.
Discussion
3589.

Assertion : Newton's third law of motion is applicable only when bodies are in motion. Reason : Newton's third law applies to all types of forces, e.g. gravitational, electric or magnetic forces.

Answer»


SOLUTION :ASSERTION is FALSE but the REASON is TRUE
Discussion
3590.

Atmospheric refraction causes advance sunrise and delayed sunset. By how much time is : (a) sunrise advanced ? (b) sunset delayed ?

Answer»


SOLUTION :NA
Discussion
3591.

List four stakeholders which may be helpful in the conservation of forests.

Answer»

Solution :The four stakeholders are :
(i)LOCAL PEOPLE living in villages near the forest.
(ii)Industrialists who use forest produce as raw materials.
(iii)Wild LIFE and nature ENTHUSIASTS.
(iv)Forest department of the GOVERNMENT.
Discussion
3592.

Define a spherical mirror. State its two types and distinguish between them.

Answer»

Solution :A mirror whose reflecting SURFACE is a part of a sphere is called a spherical mirror. Spherical MIRRORS are of two types, namely (i) concave mirror and (ii) convex mirror.
Differences between them are as follows :
`{:("""Concave mirror","""Convex mirror"),("(1) Its reflecting surface is curved inward and","(1) Its reflecting surface is curved outward"),("its centre of curvature and PRINCIPAL focus","and its centre of curvature and principal"),("are situated in front of it.","focus lie behind the mirror."),("(2) It can form real or virtual image of an object","(2) It can form only virtual image of an object"),("depending on the position of the object.","irrespective of its position."):}`
Discussion
3593.

What is meant by saying that the potential difference between two points is 1 V?

Answer»

Solution :It means 1joule of WORK is done in carrying ONE coulomb CHARGE between the two given POINTS.
Discussion
3594.

The magnetic field at the centre of the current carrying coil :

Answer»

circular
a STRAIGHT line
an ellipse
zero at the centre

Answer :B
Discussion
3595.

Environmental pollution is unnecessary and never acceptable change in the surrounding environment. True/False

Answer»


ANSWER :TRUE
Discussion
3596.

Why are the video - clips of parents threatening or hitting the childreen not studying as per their wichh or domestic helpers beating the children are very common on social meada nowadays ?

Answer»

Solution :(i) DOMESTIC violence against children has adverse effect on their PHYSICAL as well mental growth. ltbhrgt (II) If video clips of parents THREATENING or hitting the cvhildren not studying as per theirwish or domestic helpers beating the children are uploaded, the people doing such abuse will think twice before doing any such THING.
Discussion
3597.

Write down the applications of echo.

Answer»

Solution :Applications of echo:(i) Some animals communicate with each other over long distances and also locate objects by sending the sound signals and receiving the echo as reflected from the targets.
(ii) The principle of echo is used in obstetric ultrasonography, which is used to create real-time visual images of the developing EMBRYO or fetus in the mother.s uterus. This is a SAFE testing tool, as it does not use any HARMFUL radiations.
(iii) Echo is used to DETERMINE the velocity of sound WAVES in any medium.
Discussion
3598.

Calculate maximum power of accomodation of a person having normal vision.

Answer»

Solution :For a PERSON having normal vision, least distance of DISTINCT vision d = 25 CM = 0.25 m.
So, maximum power of accomodation,
`P = (1)/(f("in mm")) = (1)/(d) = (1)/(0.25) = 4D`
Discussion
3599.

Amphibia and Reptilia .

Answer»

SOLUTION :
Discussion
3600.

Saving energy is the need of the hour.

Answer»

Solution :(a). Due to high energy consumption the existing sources of energy are depleting RAPIDLY and will become scarce in the future.
(b). Saving energy will reduce the burning of fossil fuels thus minimizing air pollution, water pollution and production of harmful GASES that lead to environmental HAZARDS such as global WARMING and acid rain.
HENCE, saving energy is the need of the hour.
Discussion