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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 251. |
What is the reason for the twinkling of stars? |
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Answer» Exposions occourring in stars from TIME to time. |
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| 252. |
What will happen in future if animal species continue to go extinct ? |
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Answer» Solution :i. Humans are constantly interfering with or invading the natural habitats of plants and animals. It is one of the major reasons forextinction of animal species. ii. If animal species GET EXTINCT, then it firectly affects its predators , thereby decreasing the population of its predators too. Eventually, this disrupts the whole food chain. III. In a food WEB, different food chains are interlinkedi.e., an animal is dependent on another animal for food which is a source of food for many other animals. iv. If the EXTINCTION of animal species continues with this ratethe rate wildlife would be lost and this will degrade the environment. |
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| 253. |
A bullet of a mass 0.02 kg is moving with a speed of 10ms^(-1). It can penetrate 10 cm of a wooden block, and comes to rest. If the thickness of the target would be 6 cmonly, find the K.E. of the bullet when it comes out. |
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Answer» SOLUTION :For x=10cm =0.1 m `Fx=1/2mv_(1)^(2)=1J` `:.F=10N` For x=6cm=0.06m,`Fx=1/2mv_(1)^(2)-1/2mv_(2)^(2)` or `Fx=1/2mv_(1)^(2)-` FINAL K.E. or Final K.E.`=1/2mv_(1)^(2)-Fx=1-10xx0.06` `=1-0.6` `=0.4J` |
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| 254. |
Mention why is it not possible to make use of solar cells to meet all our energy needs. State three reasons to support your answer. |
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Answer» Solution :(i) Availability of special grades silicon used for making SOLAR cells is LIMITED. (II) Silver is used for the inter-connection of the cells in the panel which adds to its cost. (III) Low efficiency of solar cells is another reason. |
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| 255. |
How can you relate the formation of water droplets on the outer surface of a bottle taken out of a refrigerator with formation of dew ? Also explain what is dew point? |
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Answer» Solution :At a given temperature, there is a LIMIT on how much water vapour the given volume of air can hold. The lower the temperture , the lower is the capacity of air to hold water vapour. The temperature of a bottle kept in a REFRIGERATOR is lower than room temperature . Hence,when the bottle is taken out of the LEFT refrigerator, the temperature of air surrounding the bottleis lowered. Therefore, the capacity of the air to hold water vapour becomes less.Hence, the excess water vapour CONDENSES to FORM water dropletes ( like dew) on the outer surface of the bottle . |
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| 256. |
A body starts from rest and its distance covered in n" second is given by S_(n^(th)) =(a)/(2) (2n-1) ,when 'a' is acceleration of the body. Then SI unit of S_(n^(th)) is |
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Answer» m |
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| 257. |
Which of the following sinks in water ? |
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Answer» WOODEN block |
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| 258. |
First vascular plants are |
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Answer» Solution :(a) In `F_1` generation, all PLANTS are tall (TT) (b) In `F_2` generation the ratio of tall plants to dwarf PLANT is 3:1. i.e. 3 tall and 1 dwarf Three types of plants were obtained Tall homozygous: TT - 1 Tall heterozygous: Tt - 2 Dwarf homozygous: tt-1  Dawrf plants were missing on `F_1`but reappered in `F_2` generation . (ii) Sino-artial nole acts as the pacemaker of the HEART becuase it is caplable of intiating implulse which can stimulate the heart muscles to coantract . |
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| 259. |
Nametwolayeredprotectivecoveringofhumanheart. |
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Answer» PLEURAL membrane |
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| 260. |
Draw the pattern of magnetic field lines produced around a current- carrying straight conductor passing perpendicularly through a horizontal card-board. |
| Answer» SOLUTION :SEE Fig13.19 | |
| 261. |
Pressure at a depth 'h' in a liquid is …………. |
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Answer» <P>`P=P_(@)+hrhog` |
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| 263. |
State whether the following statement is true or false ? If the angle of incidence is greater than the critical angle, light is not refracted at all, when it falls on the surface from a denser medium to a rarer medium. |
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Answer» |
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| 264. |
State the factors responsible for environment pollution. |
| Answer» Solution :The factors RESPONSIBLE for ENVIRONMENTAL pollution are population explosion , RAPID industrialization , indiscriminate use of NATURAL resources, deforestation and unplanned urbanization. | |
| 265. |
An electric heater of resistance 8Omega draws 15 A from the service mains 2 hours. Calculate the rate at which heat is developed in the heater. |
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Answer» SOLUTION :`P=E/t=(I^(2)Rt)/t=I^(2)R=15xx15xx8=1800W` So, HEAT is developed at a RATE of 1800 J/sec. |
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| 266. |
Explain the use of concave lenses in the following: Peephole in door |
| Answer» Solution :(b) The peephole in DOOR - This is a SMALL safety DEVICE which HELPS us see a large area OUTSIDE the door. This uses one or more concave lenses. | |
| 268. |
List two problemsthat may arise by planting trees of single variety over vasts tracts of a forest. |
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Answer» Solution :(i)Loss of BIODIVERSITY (ii)Varied needs of the LOCAL people can no LONGER be met. (iii)Degradation of soil. |
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| 269. |
State the factors on which the moment of inertia of a body depends. |
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Answer» SOLUTION :(i) MASS of body (II) Size and shape of body (iii) Mass distribution w.r.t. AXIS of rotation. (iv) Postion and orientation of ROTATIONAL axis. |
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| 270. |
A crane pulls up a car of mass 500 kg toavertical height of 4 m. Calculate the work done by the crane. |
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Answer» Solution :In order to RAISE the car, the CRANE has to do work against the force of GRAVITY. Therefore, the force REQUIRED to lift the car F = MG `=500xx9.8=4900 N` Displacement S = vertical height moved = 4 m. Work done W = F S = `4900 xx 4` = 19600 J |
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| 272. |
A boat is moving with a velocity (3hati+4hatj) with respect to ground. The water in river is flowing with a velocity (-2hati-4hatj) with respect to ground. What is the relative velocityof boat with respect to river ? |
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Answer» SOLUTION :`vecV_(BW)=vecV_(B)-vecV_(W)` `vecV_(BW)=5i+8j`. |
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| 273. |
Principal focus of concave lens: |
Answer» Solution :Rays TRAVELLING PARALLEL to the principal AXIS of a concave LENS diverge after refraction in such a WAY that they appear to be coming out of a point on the principal axis. This point is called the principal focus of the concave lens. 
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| 274. |
Draw a figure explaining various terms related to a lens. |
Answer» Solution :Concepts related to lens: (i) Centre of curvature (C): The CENTRES of spheres whose parts form surfaces of the lenses are called centres of curvatures of the lenses. A lens with both surfaces spherical, has two centres of curvature `c_(1) " and " c_(2)` (ii) Radius of curvature (R): The radii `(R_(1) " and R_(2))`of the lens. (iii)Principal axis: The imaginary line passing through both centres of curvature is called the principal axis of the lens. (iv) Optical centre (0): The point inside a lens on the principal axis, through which light rays pass without changing their path is called the optical centre of a lens. In figure 7.14, rays` P_(1) Q_(1)`, `P_(2)Q_(2)` passing through O are GOING along a straight line. Thus, O is the optical centre of the lens.  (v) Principal focus (F): When light rays parallel to the principal axis are incident on a convex lens, they converge to a point on the principal axis. This point is called the principal focus of the lens. As shown in figure 7.15a `F_(1)" and "F_(2)` are the principal foci of the convex lens.  Light rays parallel to the principal axis falling on a convex lens COME together , i.e. get focused at a point on the principal axis . So , this type of lens is called a converging lens. Rays travelling parallel to the principal axis of a concave lens diverge after refraction m such a way that they appear to be coming outof a point on the principal axis. This point is called the principal focus of the concave lens. As shown in figure 7.15 (b) `F_(1)" and "F_(2)` are the principal foci of the concave lens. Light rays parallel to the principal axis falling on a concave lens GO away from ONE another (diverge) after refraction. So, this type of lens is called a diverging lens. (vi) Focal length (L): The distance between the optical centre and principal focus of a lens is called its focal length. |
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| 275. |
Genetically modified crops |
| Answer» Solution :Crops having desired characters are DEVELOPED by INTEGRATING FOREIGN gene with their genome, such crops have modified genome and are KNOWN as genetically modified crops. | |
| 276. |
The image of a candle flame placed at a distance of 45 cm from a spherical lens is formed on a screen placed at a distance of 90 cm from the lens. Identify the type of lens and calculate its focal length. If the height of the flame is 2 cm, find the height of its image. |
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Answer» Solution :As the image is being formed on a screen, the image MUST be a real image and the lens used must be a convex lens. As per question with sign convention : U = - 45 CM, V = + 90 cm and h = + 2 cm. `therefore""(1)/(f) = (1)/(v) - (1)/(u) = (1)/((+90)) - (1)/((-45)) = (1)/(90) + (1)/(45) = (1 + 2)/(90) = (3)/(90) = (1)/(30)` `rArr""f = + 30` cm If height of the image be h., then `(h.)/(h) = (v)/(u)` `rArr""h. = (v)/(u).h = ((+90))/((-45)) XX 2 = - 4` cm |
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| 277. |
Figure shows a ray of light as it travels from medium A to medium B. Refractive index of the medium B relative to medium A is |
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Answer» `SQRT(3)//sqrt(2)` |
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| 278. |
Choose the correct alternaive and write the alphabet corresponding to the correct answer: ………… is an allotropic from of a nonmetal which conducts electricity . |
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Answer» SULPHUR |
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| 279. |
Gluconeogenesis is the |
| Answer» SOLUTION :Formation of GLUCOSE through non-carbohydrate SOURCES such a protein is CALLED GLUCONEOGENESIS. | |
| 280. |
Name any two appliances /devices based on heating effect of current. |
| Answer» SOLUTION :Electric IRON,electric toaster,electric OVEN ETC | |
| 281. |
In which condition is the magneticforce actingona given current - carryingrod placed in a magneticfield maximum andin which condition wouldthe magneticforce not act on the rod ? (Assume that the current through the rod and the strength of the magnetic fieldare notchanged). |
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Answer» Solution :(1) Whenthe DIRECTIONOF theelectric currentpassing through the rod is PERPENDICULAR to the directionof the magnetic field, maximumforceis exertedon the rod. (2)Whenthedirection of the electric currnetis the sameas THATOF the magneticfieldor isoppositeto thatof the magnetic field, noforceis EXERTED on the rod. 
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| 282. |
............ are used in domestic appliances like mixers, washing machines and refrigerators |
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Answer» AC motors |
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| 283. |
Can any energy source be pollution free ? Why or why not? |
| Answer» Solution :No energy source can be pollution free. It is considered that SOLAR cells are pollution free. However, even thelr making causes environmental damage INDIRECTLY. In the case of nucear energy, there is no waste PRODUCED after the fusion reactions. However, it is not totally pollution free. To start the fusion reaction, approximately 107 K TEMPERATURE is required. which is provided by fission reactions. The wastes released from fission reactions are very hazardous. Hence, no energy source is pollution free. | |
| 284. |
What is biomass? Explain the principle and working of a biogas plant using a labelled schematic diagram. |
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Answer» Solution :Biomass refers to those living and non-living organic materlals that can be used as energy sources in the form of a fuel. Some examples of biomass fuels are biogas, wood , crops, and organic garbage. The chemical energy in biomass is released as HEAT on burning. Biomass refers to the organic fuel obtained from plant wastes and ANIMAL wastes like cowdung residue after harvesting8 crops, vegetable waste, SEWAGE, etc. It has been used as a fuel for a long time. These fuels, however, do not produce much heat on burning and give a lot of smoke when burnt.  Principle When substances likes cowdung vegetable waste, etc undergo anaerobic [in absence of air] decomposition, these COMPLEX substances are broken down into simpler substances and gases like methane, carbon dioxide, etc., are produced. Working The plant has a dome-like brick structure. A slurry of cowdung and water is made In the mixing tank from where it is fed into the digester. The digester is a sealed chamber in which there is no oxoygen. Anaerobic microorganisms decompose or break down complex compounds of the cowdung slurry. lt takes a few days for the decomposition PROCESS to be complete and generate gases like methane, carbon dioxide, hydrogen, and hydrogen sulphide. The biogas is stored in the gas tank above the digester from which it is drawn through pipes for use. |
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| 285. |
What is absolute refractive index? |
| Answer» Solution :When -first medium is taken as VACUUM, the refractive index of second medium is called as absolute refractive index. 8. An image formed in a spherical mirror has MAGNIFICATION: -2. Is the image REAL or virtual? The image is real. | |
| 286. |
A charged particle placed in a uniform magnetic field experiences : |
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Answer» A force in the DIRECTION of the field |
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| 287. |
The force of attraction due to a hollow spherical shell of uniform density on a point mass situated inside is zero, so can a body be shielded from gravitational influence? |
| Answer» Solution :No, the GRAVITATIONAL force is INDEPENDENT of INTERVENING MEDIUM. | |
| 288. |
What will be the effect on horizontal range of a projectile when its initial velocity is doubled, keeping the angle projection same ? |
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Answer» Solution :`R=(u^(2)sin 2 THETA)/(g)rArr R prop u^(2)` Range BECOMES FOUR times. |
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| 289. |
What is meant by Natural Radioactivity ? |
| Answer» Solution :This PHENOMENON of SPONTANEOUS emission of RADIATION from certain elements on their own is called .natural RADIOACTIVITY. | |
| 290. |
A current of 1 ampere flows in a series circuit containing an electric lamp and a conductor of 5Omega when connected to a 10 V battery. Calculate the resistance of the electric lamp. Now if a resistance of 10Omega is connected in parallel with this series combination, what change [if any] in current flowing through 5Omega conductor and potential difference across the lamp will take place? Give reason. |
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Answer» Solution :Given: In a SERIES CIRCUIT containing lamp and resistor, `I=IA,R_(L)=?R_(C)=5Omega,V=10V` Using Ohm.s law, `V=1R_(S)` `V=1[R_(L)+R_(C)]` `10=1[R_(L)+5]` `R_(L)=5Omega`. So, RESISTANCE of an electrical lamp is `5Omega`. According to the given condition, circuit can be redrawn as shown.  So, effective resistance of parallel combination, `1/R_(P)=1/R_(2)+1/R_(S)` = `1/R_(2)+1/(R_(L)+R_(1))` = `1/10+1/(5+5)=1/10+1/10=1/5` Therefore, `R_(P)=5Omega` Current drawn from the battery `I=V/R=10/5=2A` As in parallel combination, potential difference across them remains same. So, `I_(1)R_(AB)=I_(2)R_(CD)` `rArrI_(1)/I_(2)=R_(CD)/R_(AB)=10/10=1` `rArrI_(1)=I_(2)` i.e., Current is divided in both the arms equally. So, `I_(1)=I_(2)=IA`. Hence, there will be no change in the current through `5Omega` conductor. ALSO there will be no change in the potential difference across the lamp as in both cases, current through the lamp remains same i.e. IA. |
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| 291. |
Match the following{:(1."Retina",-,(a)"Path way of light"),(2."Pupil",-,(b)"Far point comes closer"),(3."Ciliary muscles",-,(c)"Near point moves away"),(4."Myopia",-,(d)"Screen of the eye"),(5."Hypermetropia",-,(f)"Power of accommodation"):} |
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Answer» Path way of light POWER of accommodation Far point COMES CLOSER Near point MOVES away |
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| 292. |
An alternating current has a frequency of 50 Hz. How many times does it change its direction in one second? |
| Answer» SOLUTION :100 TIMES. | |
| 293. |
What will you do? Why? Your friend has developed the hobby of snapping selfies. |
| Answer» Solution :I would FIRST EXPLAIN my friend the hazards of snapping selfies. I will show how to stop the HABIT by involving himself/herself in sojme CONSTRUCTIVE WORK. | |
| 294. |
Whathappens when a barmagent is quicklymoved towards a coil? |
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Answer» The resistanceof the coil INCREASES . |
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| 295. |
Metal and Nonmetals. |
Answer» SOLUTION :
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| 297. |
(a) Water is an elixir of life, a very important natural resource. Your Science teacher wants you to prepare a plan for a formative assessment activity, "How to save water, the vital natural resource." Write any two ways that you will suggest to bring awareness in your neighbourhood, on 'how to save water'. (b) Name and explain any one way by which the underground water table does not go down further. |
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Answer» Solution :(a) Ways to bring about awareness on 'how to save' water: (i) We can CONDUCT door to door campaign to make people aware about the acute shortage/scarcity of water during summer. (ii) We can educate people on ways to save water, for example, close taps properly, USE bucketsof water to bathe instead of showers etc. (ii) I can ALSO suggest them how to store rainwater in the small park of our locality, so that it can be used hot summer days, when availability of water is very LESS. (b) We can also prevent the level of underground water table to not go down further by harvesting the rainwater in the underground tanks in parks and cropfields. |
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| 298. |
Thanish added acetic acid along with concentrated sulphuric acid to ethanol what would be his observation during the experiment ? |
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Answer» Solution :1) He MAY OBSERVE that the resulting mixture is a sweet odoured SUBSTANCE. 2) The substance is ethyl ecetate, an ester. |
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| 299. |
About which axis a uniform cube will have minimum moment of inertia ? |
| Answer» SOLUTION :It will be about an AXIS PASSING through the centre of the cube and connecting the opposite CORNERS. | |
| 300. |
What name is given to the heat energy obtained from hot rocks inside the earth ? |
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