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Adioptre(uk), ordiopter(us), is a unit of measurement of the optical power of a lens or curved mirror, which is equal to the reciprocal of the focal lengthmeasured in metres (that is,1/metres). It is thus a unit of reciprocal length.1 dioptre is SI unit of the power of a lens whose focal length is 1 metre. It is denoted by the letter D. Thus 1D = 1 m-1. Simply, when focal length ‘ f ‘ is expressed in metres, then, power is expressed in dioptres. The power of a convex lens is positive and that of a concave lens is negative.

Thefocal lengthof aspherical mirroris notaffectedwhen it isimmersed in water- it remains same. Laws of reflection are independent of medium and hence reflection takes place in any medium without the change offocal length. But, in case of LENS, thefocal lengthchanges.

can you answer the second bit

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Η=F×r÷Avf=tangential force,r=distance between the layer , v=velocitydimensional formula for force = M¹L¹T⁻²dimensional formula for area = M⁰L²T⁰dimensional formula for distance = M⁰L¹T⁰dimensional formula for velocity = M⁰L¹T⁻¹η= M¹L¹T⁻²ₓ M⁰L¹T⁰÷M⁰L²T⁰ₓ M⁰L¹T⁻¹=M¹L⁻¹T⁻¹dimensional formula for coefficient of viscosity =M¹L⁻¹T⁻¹and SI unit of coefficient viscosityη=pascal second

If α is the temperature coefficient of resistance, R' is the initial resistance at initial temperature, then we know that:

R=R'(1+α ΔT)

where ΔT= Final temperature- initial temperature

Change in temperature is (500-20) =480 degrees

Initial Resistance= 20 ohm

Final resistance =60 ohm

Thus,

60=20(1+(α.480))

From this,

α=0.004166 /C =0.4166 X 10^(-2) /C

Now: The temperature at which its resistance is 25 ohm:

R=R'(1+α ΔT)

25=20(1+ (0.004166)(T-20))

Thus, T= 80 degrees

when lift goes downwards then seudo force acts on boy in upward direction...

if a is the accleration of lift then

mg - ma = net weight=30g ...........1 (given) g is accleration due to gravity

m(g-a) = 30g

m=40kg

when lift goes upward then seudo force acts in downward direction so now net weight

mg + ma = W

40(a+g) = W

50kg = W

pressure = force/ area50/0.5100N/m^2

we will use Snell's law n1sin∅1 = n2sin∅2 n1 = x , sin∅1 = 45° , n2=4/3 and sin∅2 = 90°( for total internal reflection)

so, n1sin∅1 = n2sin∅2 => x*(1/√2) = (4/3)*(1) => x = 4√2/3

option 1

When block is displaced by the displacement l then

Change in potential energy = gain in kinetic energy

Mgl = 1 / 2 mv^2

V= square root of 2gl

Hence, the answer is square root of 2gl

mass=m=10kgg=10m/s²length=40mh=20mTension at a point h meter height from the lower end of the rope=mgh

the speed of transverse wave V=√(T/m)=√[mgh/m]=√ghSubstituting values:V=√[10x20)=10*(2^0.5) m/s

20 is the correct answer of the given question

20 times because it rotates and passes an electric appliance by two times as they were 10 appliances

Newton's law of universal gravitation states that every particle attracts every other particle in the universe with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers.

1.cereal crop= wheat,berley, corn2.pulses=garden peas,black gram,kedneysbeans3.oil seads=mustard,sunflower, castor

4.vegetables=tomato,potato,cabbage5.fruit= mango,guava,grapes6.plantations crops = tea ,coffe,rubber7. spice crops=chillies,ginger,turmeric ,colves8.fibres crops=cotton,hemp,jute.

i have also first ans.

Using symmetry here we see that that all froces

=) F1 = F2 = F3 = kQq/r^2

here r = AO = BO = CO

using trigonometry we can find " r "

Here we can see that length of each side of ∆ ABC is " L "

=) In ∆ BOD

Angle OBD = 30°

and BD = L/2

COS 30 ° = L/2r =) r = L/2 × sec30°

=). r = L/2 × 2/√3 = ( 1/√3 ) L -----(1)

so we can see tha all forces are equal

F1 = F2 = F3 = kQq/ (L/√3)^2 = 3kQq/L^2

and angle between each forces is 120°

using Lami's theorem if all forces are equal in magnitude and angle between then is also equal and planar then resultant force is 0

=) Fnet = F1 +F2 + F3 = 0

=) here we add forces using vectors to get net force = 0

so Net force on charge " Q " placed at centroid is zero.

(a) Uniform Velocity - A body is said to have uniform velocity if it covers equal distance in equal intervals of time in a particular direction, however the time intervals may be small

(b) Variable Velocity - When a train stops in a platform its velocity changes in every moment. Its an example of variable velocity.

(c) Example of variable acceleration are velocity increases in unequal amount with equal interval. For example, a car is moving in a crowded street, when car find space it will move with greater speed and if it stuck in crowd then it will move with less speed.

(d) Examples of uniform retardation are:1) Velocity of vehicle decreases when brake is applied.2) Landing of aeroplane. 3) When fan is switched off. 4) A train reaching at a station.

uniform velocity-A bus travelling towards east with a speed of 20km/hvariable velocity-A car travels with a 20km/h east,then turns to north with different speed or same speedvariable acceleration - A bus accelerates for 2m/s^2 and then accelerates for 10m/s^2uniform retardation- A bus applies brakes and comes to test with a uniform retardation of 5m/s^2

Increase = l*a*temperature change= 0.5*0.00001*20= 0.0001m

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7A+7A=14A=6+15=21;; A=21/14=3/2

8 ohm is the answer to the questionas 2+2+2+2= 8 ohmfor parallelconnection3*6/3+6= 18/9= 2 ohm

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Option (a) 5ohom is the following question answer

option A correct answer

5 ohm is correct answer of this problem.

you can take a voltage source across ab and by symmetry you can write current in circuit the R = V/I will be the answer

H=U²Sin²θ/2gT=2Usinθ/gnow if we take the ratio ofmaximum height reached to the square of flight time:H/T²=U²Sin²θ/2g/4U²sin²θ/g²=g/8If we take g=10 m/s² thenH/T²=10/8=5/4

The order of the magnitude of acceleration due to gravity is , 10^1.

Thermometers are used to see if you have a fever or tell you how cold it is outside. Made up of thermo (heat) and meter (measuring device), the meaning of the word thermometer is pretty straightforward.Thermometers measure temperatures in degrees, according to either the Celsius or Fahrenheit system.

Therefore, Thermometer is a device used for measuring body temperature.

Thermometer is used to measure temperature

Newton's First Law states that " every object which is at rest or uniform motion continues to be in state of res or uniform motion unless compelled to change its state by action of net force."

Example:A space craft far from any source of gravity would need no thrust to keep it moving at a constant speed in a given direction.Once set in motion, it continues to move forever without propulsion since there is no friction is space.

Second law of motion " Rate of change of momentum of the body is directly proportional to the force acting on it."

Example:Fielder in a cricket match pulls his hand backwards to reduce impact of impulse force.Working of air bags to prevent the time of injury.Objects in our room remain as it is unless a force as on it act.If we shake a tree, the fruits at rest will fall down.

Third law of motion states " For every action there is equal and opposite reaction "Example:Working Principle of Rocket.Recoil of a gun.

charge in electron -1.6*10^-19Cnumber of electrons=total charge/charge of an electron=-1*10^-6/-1.6*10^-19=0.625*10^13electrons

thanks ji Ram Ram ji

3) is correct answer

answer 3 is the right ans

option 3re is correct