9264 + Interview Questions in Physics in Class 10 Page 158 InterviewSolution

7851.	The image of an object formed by an optical device is always virtural and small. The device may be
Answer» A convex lens a CONCAVE mirror a glass plate a concave lens Solution :Out of given optical devices only a concave lens can ALWAYS form a virtual and small sized image of an object PLACED in FRONT of it.

Discussion

7852.	You must have seen chandeliers having glass prism. The light from a tungsten bulb gets dispersed while passing through these prismsand we see coloured spectrum. If we use on LED light instead of tungsten bulb, will we be able to see the same effect ?
Answer» Solution :Yes, We can see the same effect for LED LIGHT also. But the SPECTRUM obtained is not continuous as in the case of SUNLIGHT.

Discussion

7853.	Why an astronaut in an orbiting space craft is not zero gravity although he is in weight lessness?
Answer» SOLUTION :The ASTRONAUT is in the gravitational field of the earth and experiences gravity. However, the gravity is used in providing NECESSARY CENTRIPETAL force, so is in a state of free fall TOWARDS the earth.

Discussion

7854.	A person has normal vision, but he cannot distinguish between red-green colours. Why ?
Answer» SOLUTION :A person who is blind to red-green colours MAY be deficient in cone shaped cells having red and green PIGMENT in the retina of his eyes. It is a genetic disorder and not a refraction defectof VISION. That is why, such a person may have normal vision.

Discussion

7855.	Focal length of a glass lens in air is 2.5 cm. Its focal length when immersed in water would be
Answer» `2xx2.5cm` `4xx2.5cm` `6xx2.5cm` `(2.5/4)CM` ANSWER :B

Discussion

7856.	Write the full name of the technique used in locatingan under-water obstacle
Answer» SOLUTION :SONAR `→` SOUND NAVIGATION and RANGING.

Discussion

7857.	A metal 'M' is in the first group of the periodic table. What will be the formula of its oxide ?
Answer» `MO` `M_(2)O` `M_(2)O_(3)` `MO_(2)` SOLUTION :`M_(2)O`

Discussion

7858.	A full length image of a distant tall building can definitely be seen by using
Answer» a concave mirror a convex mirror a plane mirror both concave as well as convex mirrors Solution :A full length image of a distant tall building can defiitely be seen by USING a convex mirror because a convex mirror always FORMS a VIRTUAL erect and highly DIMINISHED image.

Discussion

7859.	Out of the two elements A and B with mass number 2 and 235 respectively, which one is suitable for making : (i) a nuclear reactor (ii) a hydrogen bomb. Name the nuclear reaction involved in each case. Write one difference between the two types of nuclear reactions.
Answer» Solution :Nuclear REACTOR : ELEMENT B Process : Nuclear FISSION Hydrogen BOMB : Element A Process : Nuclear Fusion Nuclear

Discussion

7860.	Name the type of asexual reproduction in which two individuals are formed from a single parent and the parental identity is lost. Draw the initial and the final stages if this type of reproduction. State the event with which this reproduction starts.
Answer» SOLUTION :The type of asexual reproduction is binary fission. This reproduction STARTS with ELONGATION of nucleus.

Discussion

7861.	What is an electromagnet ? How can we determine north and south pole of an electromagnet with the help of magnetised iron bar?
Answer» Solution :An ELECTROMAGNET is a solenoid coil that attains magnetism DUE to flow of current It works on the principle of magnetic effect of current. (i) By suspending magnetised bar and IDENTIFY its north and south poles. (II) By finding the polarity of electromagnet USING the property-like poles repel.

Discussion

7862.	If the absolute refractive indices of glass and water are 3/2 and 4/3 respectively, what is the refractive index of glass with respect to water?
Answer» SOLUTION :Given : ABSOLUTE Refractive index of glass `(""_(g)n_(v))=3//2` Absolute refractive index of water `(""_(W)n_(v))=4//3` To find : refractive index of glass with respect to water `(""_(g)n_(w))` Formula : `""_(2)N=v_(1)/(v_(2))` Solution : Refractive index of glass with respect to water `""_(g)n_(w)=""_(w)n_(v)//""_(g)n_(v)` `(3/2)/(4/3)=(9)/(8)` Refractive index of glass with respect to water is `(9)/(8)`

Discussion

7863.	Butterfly is a "_________________" consumer
Answer» primary Secondary tertiary none of these Answer :A

Discussion

7864.	Whether there hand been mock drill by fire fighters under the disaster management scheme in your school? Which techniques did you see during the drill?
Answer» Solution :Some of the fire fighting techniques demonstrated durign the mock drill are: i. EXTINGUISHING fires based on the cause of fire. ii. Rescuingthe PEOPLE TRAPPED at higherfloors of buildings and taking them to safe place. iii. Rescuing the persons WHOSE CLOTHING has caught fire. iv. Evacuation and assembly in open spaces/ grounds. v. First aid skills. vi. Raisig an alarm in case of emergency.

Discussion

7865.	In frogs, …………., is absent .
Answer» SOLUTION :In FROGS, NECK is ABSENT .

Discussion

7866.	What is hypocotyls ?
Answer» SOLUTION : Hypocotyl is the embryo axis between the RADICLE and the POINT of attachment.

Discussion

7867.	An image 2/3 of the size of the object is formed by a convex lens at a distance of 12 cm from it. Find the focal length of the lens.
Answer» Solution :The IMAGE formed is REAL (CONVEX lens forms `m=-2/3,v=+12cm,m=v/u-2/3` `-2u=36` `u=-18cm` `1/f=1/v-1/u` `1/f=1/12-1/(-18)` `=(3+2)/36` `f=36/5=7.2cm`

Discussion

7868.	Explain how concave lenses are used in the following devices. Spectacles
Answer» Solution :SPECTACLES: NEARSIGHTEDNESS is corrected USING spectacles having concave lenses.

Discussion

7869.	List two characteristics of the material used in a fuse wire.Name the material it is made of . A fuse is alwaysconnected in series in an electric circuit. Justifythis statement giving reason.
Answer» Solution :The material used in the fuse wire should have a low meltingpoint and a low resistance. Generally, the fuse wire is thin, made of copper, aluminium, iron, ETC., all tin-PLATED or lead- plated. If a fuse is connected in series, the fuse wiremelts when a high current FLOWS and the CIRCUIT is broken. If it is connected in parallel, even if the fuse melts, current flows the remainingpart of the circuit . Thus, a fuse is always connected in series.

Discussion

7870.	Choose the wrong statement:
Answer» the ACCELERATED MOTION may be due to change in magnitude of velocity or direction of velocity or both. the velocity and ACCELERATION of a body may not necessarily be in the same direction the velocity and acceleration of a body may not be ZERO simultaneously. when a body falls FREELY under the action of gravity, its acceleration is zero. Solution :when a body falls freely under the action of gravity, its acceleration is zero.

Discussion

7871.	Is it true that the construction of turbine is different for different types of power plants? Explain with an example.
Answer» Solution :(1) Generators work on the PRINCIPLES of electromagneticinduction. For this the generator must be rotated. (2) For this purpose, there is a turbine for each generator. (3) For rotation of a turbine, energy is needed . (4) The TURBINES are different ACCORDING to the TYPE of energy source that is used for its rotation.Therefore, the construction of turbine isdifferent for each power plant.

Discussion

7872.	A laser light beamed at themoonthe takes2.56 sto returnafter reflectionat the moon's surface . How much isthe radius of thelunar orbit around the earth ?
Answer» SOLUTION : `t=2.56s` `therefore` t = time taken by laser beam to go to the moon = `(t)/(2)` distance between EARTH and moon `=d=cxx(t)/(2)` `=3XX10^(8)xx(2.56)/(2)` `=3.84xx10^(8)m`.

Discussion

7873.	Is the acceleration of a particle in circular motion not always towards the centre. Explain.
Answer» Solution :No acceleration is TOWARDS the CENTRE only in case of UNIFORM CIRCULAR MOTION.

Discussion

7874.	If 10 mL of H_(2)SO_(4)is mixed with 10 mL of Mg(OH)_(2)of the same concentration, the resultant solution will give the following colour with universal indicator :
Answer» Red Yellow Green Blue Solution :PH = 7

Discussion

7875.	If calorie heat is produced by spending mechanical work W then mechanical equivalent of heat J=Wxx Q
Answer» SOLUTION :`J=(W)/(Q)`

Discussion

7876.	What do you conclude form the above activity?
Answer» Solution :We observe that VIBRATING TUNING fork PRODUCES SOUND.

Discussion

7877.	How will the image formed change when an object is moved gradually close to convex lens?
Answer» Solution :As the object is moved gradually close to the CONVEX lens, the changes in the image formed will be as follows, 1. The size of the image will INCREASE gradually. 2. The POSITION of the image will be shifted away from the lens. 3. The nature of image remains real and inverted till the position of object is not within its LOCAL length. Therefore, the image will be virtual and erect.

Discussion

7878.	The term biogenesis was coined by
Answer» LOUIS PASTEUR Darwin Lamark Oparin Answer :A

Discussion

7879.	A total reflecting right angled isosceles prism can be used to deviate a ray of light through :
Answer» `30^(@)` `60^(@)` `75^(@)` `90^(@)` ANSWER :D

Discussion

7880.	What is diaphragm?
Answer» Solution :Diaphragm is the CHARACTERISTIC feature of MAMMALS. It is a muscular membrane that separates the THORACIC cavity from abdominal cavity.

Discussion

7881.	The adjacent Figure shows a fixed pulley used by a boy to lift a load of 400 N through a vertical height of 5 m in 10 s. the effort applied by the boy on the other end of the rope is 480 N. (a) What is the velocity ratio of the pulley ? (b) What is the mechanical advantage ? (c) Calculate the efficiency of the pully. (d) Why is the efficiency of the pulley not 100% ? (e) What is the energy gained by the load in 10 s? (f) How much power was developed by the boy in raising the load ? (g) The boy has to apply an effort which is greater than the load he is lifting. what is the justification for using the pulley ?
Answer» Solution :(a) When the effort moves a distance d downwards, the load moves a distance d UPWARDS. Velocity ratio=`("displacement of effort")/("displacement of load")=(d)/(d)=1` (b) Mechanical advantage=`("load")/("effort")` or `M.A.=(400)/(480)=(5)/(6)=0833` (c) Efficiency `eta=(M.A.)/(V.R.)=(0833)/(1)=0*833` or 83.3% (d) The efficiency is less than 100% because some energy is wasted in overcoming the friction of the pulley bearings. (e) Energy gained by the load =load`xx`displacement of load `=400xx5=2000J` (f) Power developed by the boy `=("effort"xx"displacement")/("time")` `=(480xx5)/(10)=240W` (g) Use of pulley HELPS in changing the direction of the applied FORCE to a convenient direction (instead of upward direction to downward direction). so one may also use his/her own WEIGHT as effort.

Discussion

7882.	(a) What is an armature ? What its advantage ? (b) What are the advantage of electromagnet over permanemt magnet ?
Answer» Solution :The soft iron core, on which the coil is wound plus the COILS is called an armature. It is used in electric motors to act as an electromagent The armature enhances the power of the motor (ii) The advantages are You can TURN the electromagnet by switching ON or OFF the current You can reverse the POLES of the electromagent by REVERSING the direction electric current flow in the coil The magnetic field strength can be changed by changing the amount of current in the coil. An electromagnet can easily be made more POWERFUL than a permanent magnet

Discussion

7883.	n resistors, each of resistance R are first connected in series and then in parallel. What is the ratio of the total effective resistance of the circuit in the series to the parallel combination?
Answer» SOLUTION : In the SERIES COMBINATION, `R_s = NR` In the PARALLEL combination, `R_p = R/n` `:. R_s/R_p =(nR)/(R//n) =n^2`

Discussion

7884.	Explain about domestic electric circuits. (circuit diagram not required)
Answer» Solution :(i) Electricity is distributed through the domestic CIRCUITS wired by the electricians. (ii) The FIRST stage of the domestic circuit is to bring the power supply to the main - box from a distribution PANEL, such as a trnsformer. (iii) The important components of the main - box are (i) a fuse box and (ii) a meter. The meter is used to record the consumption of electrical energy. (vi) The fuse box contains either a fuse wire of a miniature circuit BREAKER (MCB). (v) The function of the fuse wire or a MBC is to protect the house hold electrical appliances from overloading due to excess current.

Discussion

7885.	Give the significanceof theelectricmeter in a domestic circuit.
Answer» Solution :Electric METER is used to RECORD the CONSUMPTION of electricalenergin kWh [unit] (comsumption unit ofelectrical energy) in the domesticcircuit.

Discussion

7886.	The decaying process of C-14 occurs continuously from the dead remains of living organisms. True/False
Answer» ANSWER :TRUE

Discussion

7887.	The density of nuclear matter is
Answer» EXTREMELY SMALL small LARGE extremely large SOLUTION :extremely large

Discussion

7888.	A spherical mirror and a thin sperical lens have each a focal length of -15 cm. The mirror and then lens are likely to be
Answer» Both concave Both CONVEX The mirror is concave and the LENS is convex The mirror is convex, but the lens is concave Solution :FOCAL LENGTH of a concave lens and a concave mirror are taken negative as per sign convention followed.

Discussion

7889.	An electric kettle of 2kWfor 2h daily. Calculate the (i) energy consumed in SI and commerical unit, (ii) cost of running it the month of June at the rate of Rs 3.00 per unit?
Answer» Solution :Here Power P=2kW time of use t=2h DAILY `therefore` Total time of use in the MONTH of June `t=2 times 30=60h` `therefore` (i) Energy CONSUMED `E=P times t=2kW times 60h=120k Wh=120 units` `implies E=120 times 3.6 times 10^6 J=4.32 times 10^8 J` (ii) COST @ Rs 3.00 per unit `=3 times 120= 360`

Discussion

7890.	How is the excessive use of social media and technology proving harmful?
Answer» Solution :Excessive use of social media and modern technology is disturbing the social HEALTH. It is also affecting physical and mental health. Increase in cybercrimes TAKE place. PEOPLE waste their time by· watching useless and obscene material. Violence develops by watching few weird cartoon serials. DEPENDENCY on MACHINE rises and persons lose self-reliance.

Discussion

7891.	For the same angle of incidence of 45^(@), the refraction angle in two transparent media P and Q is 20^(@) and 30^(@), respectively. Which medium is optically denser out of P and Q and why ?
Answer» Solution :Medium P is OPTICALLY denser than Q because in it the RAY is bending more TOWARDS the NORMAL (As `ANGLE r_(P) lt angle r_(Q)`)

Discussion

7892.	What could be the reason ?
Answer» Solution :1) The reason for BREAKING up of the plate is the potential ENERGY of the metal BALL. 2) The reason for moving the toy car is the potential energy of the spring in the toy.

Discussion

7893.	Which of the following lenses would you prefer to use while reading small letters found in a dictionary ?
Answer» A convex lens of focal LENGTH 50 cm A concave lens of focal length 50 cm A convex lens of focal length 5 cm A concave lens of focal length 5 cm SOLUTION :A convex lens is preferred because it can form a magnified image. Moreover, we prefer lens of lower focal length (f = 5 cm), so that its POWER is large.

Discussion

7894.	What is (a) the highest (b) the lowest total resistance that can be secured by combinations of four coils of resistances 4 Omega,8 Omega,12 Omega and 24 Omega?
Answer» Solution :a) To obtain HIGHEST resistance, all the FOUR RESISTANCES must be CONNECTED in series arrangement. In that case RESULTANT resistance `R_s` is given by `R_s=R_1+R_2+R_3+R_4=4+8+12+24=48 Omega` (b) To obtain lowest resistance, all the four resistances must be connected in parallel arrangement, in that case the resultant resistance `R_p` is given by : `1/R_p=1/R_1+1/R_2+1/R_3+1/R_4=1/4+1/8+1/12+1/24=(6+3+2+1)/24=12/24` `R_p=24/12 Omega =2 Omega`

Discussion

7895.	The SI unit of electric potential is ……….. .
Answer» SOLUTION : the VOLT or the JOULE PER COULOMB

Discussion

7896.	An ice cube is floating in a glass of water. What happens to the water level when the ice melts?
Answer» RISES Falls Remains same First rises and then falls Answer :C

Discussion

7897.	The line perpendicular to the reflective surface is the _________
Answer» NORMAL Line of refraction Line of INCIDENCE Line of reflection Answer :A

Discussion

7898.	Which of the following formulae represents voltage?
Answer» `("WORK")/("current" XX "TIME")` `("Work" xx "time")/("current")` Work `xx` electric charge Work `xx` electric charge `xx` time Solution :`V = W/Q = W/(I.t) =("Work")/("electric current " xx" time")`

Discussion

7899.	What are the vaules of angle of incidence I and angle of reflection r for a normal incidence?
Answer» SOLUTION :Normal incidence implies `i=0^(@)`. Hence from the SECOND LAW of reflection `r=0^(@)`

Discussion

7900.	Overloadingis caused by connecting too many appliances in asingle socket and usingthem at the same time, How ?
Answer» ANSWER :1

Discussion

Explore topic-wise InterviewSolutions in .

The image of an object formed by an optical device is always virtural and small. The device may be

You must have seen chandeliers having glass prism. The light from a tungsten bulb gets dispersed while passing through these prismsand we see coloured spectrum. If we use on LED light instead of tungsten bulb, will we be able to see the same effect ?

Why an astronaut in an orbiting space craft is not zero gravity although he is in weight lessness?

A person has normal vision, but he cannot distinguish between red-green colours. Why ?

Focal length of a glass lens in air is 2.5 cm. Its focal length when immersed in water would be

Write the full name of the technique used in locatingan under-water obstacle

A metal 'M' is in the first group of the periodic table. What will be the formula of its oxide ?

A full length image of a distant tall building can definitely be seen by using

Out of the two elements A and B with mass number 2 and 235 respectively, which one is suitable for making : (i) a nuclear reactor (ii) a hydrogen bomb. Name the nuclear reaction involved in each case. Write one difference between the two types of nuclear reactions.

Name the type of asexual reproduction in which two individuals are formed from a single parent and the parental identity is lost. Draw the initial and the final stages if this type of reproduction. State the event with which this reproduction starts.

What is an electromagnet ? How can we determine north and south pole of an electromagnet with the help of magnetised iron bar?

If the absolute refractive indices of glass and water are 3/2 and 4/3 respectively, what is the refractive index of glass with respect to water?

Butterfly is a "_________________" consumer

Whether there hand been mock drill by fire fighters under the disaster management scheme in your school? Which techniques did you see during the drill?

In frogs, …………., is absent .

What is hypocotyls ?

An image 2/3 of the size of the object is formed by a convex lens at a distance of 12 cm from it. Find the focal length of the lens.

Explain how concave lenses are used in the following devices. Spectacles

List two characteristics of the material used in a fuse wire.Name the material it is made of . A fuse is alwaysconnected in series in an electric circuit. Justifythis statement giving reason.

Choose the wrong statement:

Is it true that the construction of turbine is different for different types of power plants? Explain with an example.

A laser light beamed at themoonthe takes2.56 sto returnafter reflectionat the moon's surface . How much isthe radius of thelunar orbit around the earth ?

Is the acceleration of a particle in circular motion not always towards the centre. Explain.

If 10 mL of H_(2)SO_(4)is mixed with 10 mL of Mg(OH)_(2)of the same concentration, the resultant solution will give the following colour with universal indicator :

If calorie heat is produced by spending mechanical work W then mechanical equivalent of heat J=Wxx Q

What do you conclude form the above activity?

How will the image formed change when an object is moved gradually close to convex lens?

The term biogenesis was coined by

A total reflecting right angled isosceles prism can be used to deviate a ray of light through :

What is diaphragm?

(a) What is an armature ? What its advantage ? (b) What are the advantage of electromagnet over permanemt magnet ?

n resistors, each of resistance R are first connected in series and then in parallel. What is the ratio of the total effective resistance of the circuit in the series to the parallel combination?

Explain about domestic electric circuits. (circuit diagram not required)

Give the significanceof theelectricmeter in a domestic circuit.

The decaying process of C-14 occurs continuously from the dead remains of living organisms. True/False

The density of nuclear matter is

A spherical mirror and a thin sperical lens have each a focal length of -15 cm. The mirror and then lens are likely to be

An electric kettle of 2kWfor 2h daily. Calculate the (i) energy consumed in SI and commerical unit, (ii) cost of running it the month of June at the rate of Rs 3.00 per unit?

How is the excessive use of social media and technology proving harmful?

For the same angle of incidence of 45^(@), the refraction angle in two transparent media P and Q is 20^(@) and 30^(@), respectively. Which medium is optically denser out of P and Q and why ?

What could be the reason ?

Which of the following lenses would you prefer to use while reading small letters found in a dictionary ?

What is (a) the highest (b) the lowest total resistance that can be secured by combinations of four coils of resistances 4 Omega,8 Omega,12 Omega and 24 Omega?

The SI unit of electric potential is ……….. .

An ice cube is floating in a glass of water. What happens to the water level when the ice melts?

The line perpendicular to the reflective surface is the _________

Which of the following formulae represents voltage?

What are the vaules of angle of incidence I and angle of reflection r for a normal incidence?

Overloadingis caused by connecting too many appliances in asingle socket and usingthem at the same time, How ?