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Law of octaves, in chemistry, the generalization made by the English chemist J.A.R. Newlands in 1865 that, if the chemical elements are arranged according to increasing atomic weight, those with similar physical and chemical properties occur after each interval of seven elements.

John Newlands, in full John Alexander Reina Newlands, (born November 26, 1837, London, England—died July 29, 1898, London), English chemist whose “law of octaves” noted a pattern in the atomic structure of elements with similar chemical properties and contributed in a significant way to the development of the periodic law.

Chemical pollution introduces chemicals into the natural environment, negatively affecting the air, water and soil. Such pollutants can come from a wide variety of sources. When chemical pollutants are concentrated or in an area for period, they can adversely affect the ecosystem and those who live in the area.

Interferenceof light waves is defined as the modification in the distribution of light energy when two or more waves superimpose each other.

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Atotally reflecting prismis that which has one of its angle equal to 90 degree and each of the remaining two angles equal to 45 degree here the phenomenon of total internal reflectionis used. The critical angle of glass is 42 degree

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An electroscope can be used to detect whether a body is charged or not. The following figure shows a simple electroscope. it consists of a metal rod. At one end of the rod, two leaves of aluminium foil are fixed and at the other end, there is a metal disc. The leaves of aluminium foil are placed inside a conical flask and the flask is corked to isolate the leaves from air.When the metal disc is touched with a charged body, the aluminium strips move away from each other. This happens because some of the charges of the body are transferred to the strips through the metal rod. This method of charging a body is called charging by conduction. The nature of charges on both the leaves and the charged body are the similar. Hence, both the leaves of the aluminium foil will move away from each other. If the body was not charged, then the leaves of the foil would remain as they were before. They would not repel each other.

So, if abodybecomes negatively chargedit will gain electrons that isits masswill increase and if abody becomes positivelychargedit loses electrons henceits masswill decrease.

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because burning of fuel cause smoke and smoke causes poplution which is bad for health

the burning of fuel can cause health hazards because burning fuel causes air pollution humans and animals also effect to lungs damage we are effect cancer etc...

The first lens is concave as the rays are diverging andthe 2nd lens is converging , that is convex lens.

Arrangement are shown in attachment . Let θ is the angle made by string with vertical . Here tanθ = perpendicular/base = √{20² - 1²}/1 = √{399} ≈ 20 e.g., cosθ = base/perpendicular = 20{approximately}/20 = 1 Hence, cosθ = 1 and sinθ = perpendicular/hypotenuse= 1/20

Now, at equilibrium Tcosθ = mg { weight } -----(1) Tsinθ = F { electrostatic force between them } ------(2)

Now, F = kq₁q₂/r² Here , q₁ = q₂ = 2 × 10⁻⁸ C and r = 3cm = 0.03 m

Now, F = 9 × 10⁹ × 2 × 10⁻⁸ × 2 × 10⁻⁸/(0.03)² = 9 × 10⁹ × 4 × 10⁻¹⁶/9 × 10⁻⁴ = 4 × 10⁻³ N

Now, Tsinθ = 4 × 10⁻³ or, T × 1/20 = 4 × 10⁻³ [ sinθ = 1/20 }or, T = 4 × 20 × 10⁻³ = 0.08N Hence, tension in string is 0.08N

Now, Tcosθ = mgor, T × 1 = m × 10 [ g = 10 m/s²or, 0.08 = m × 10 ⇒ m = 0.008 Kg

Hence, mass of each ball is 8g

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Angular speed of the rotor, ω = 200 rad/sTorque required, τ = 180 NmThe power of the rotor (P) is related to torque and angular speed by the relation:P= τω= 180 × 200 = 36 × 103= 36 kWHence, the power required by the engine is 36 kW.

'u' represents initial velocity

u represent intinal velocity

for a vector be parallel to other.. , it Should be represented in the form of K times the other vecr

here -6i+9j-12k = -3(2i-3j+4k) that is exactly k(=-3) times the earlier one..

so, both the vectors are parallel.

Do u have any other answers

At first 1μF and 3μF are in parallel the add up to 4μF , also 2μF and 4μF are in parallel , so they add up to 6μF

now 4μF and 6μF are in series with each other..

so, the equivalent capacitance is = 4*6/(4+6) = 2.4μF

54 ka

5a-6 is right answer

5a-30= 5 (a - 6) is the answer

answer=5(a-6). correct

may be, this is yr answer

5×a - 5×65(a-6)...........Please Mark as Best 😊😊

yes

yes.

kese imagine kro gye bhai

Here,Power P=400 W=400/1000 kW=0.40 kW

Time t=8 x 30=240 hours

Now electrical energy is given by,

E=P x t

=0.40 x 240=96 kWh

Thus the electric energy consumed by the refrigerator in a month of 30 days is 96 kWh.

Cost of 96 kWh of electricity=96 x 5= Rs. 480

Assuming the acceleration and retardation remain constant in both case.

Case I:

Initial velocity u=36 km/h=36*1000/3600=10 m/s.

Final velocity v=72 km/h=72*1000/3600=20 m/s.

v=u+at

a=(v-u)/t=(20–10)/5=2 m/s^2

So acceleration = 2 m/s^2

Case II:

Initial velocity u =72 km/h= 20 m/s

Final velocity v= 0 m/s

a=(v-u)/t=(0–20)/20=-1 m/s^2

acceleration= -1 m/s^2

retardation/deceleration= +1 m/s^2

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(a) is the right answer

Zero error :When the fixed stud A and movable stud B are brought in contact without applying any under pressure , and the zero of the circular scale does not coincide with the refference line, there is a zero error.

Based on the location of zero of the circular scale with respect to reference line, zero errors are further as positive or negative zero error, so while doing the calculations, in order to minimise the errors caused by the instrumental error, the positive or negative error is calculated by counting the number of divisions ahead or backward from the reference line and they are added or subtracted from the actual reading.

1

the acceleration due to gravity on moon is g ' and that on earth is g.We know that,g = GM/R2where,G > gravitation constantM > mass of earthR > radius of earthlet us introduce a new parameter, D = diameter of earth = 2R=> R = D/2

so,g '= 4GM/D2................(1)

also,g ' = Gm/r2where,G > gravitation constantm > mass of moonr > radius of moonlet us introduce a new parameter, D = diameter of moon =2r=> r = d/2

so,g '=4Gm/d2................(2)

Now,it is given,M:m = 80:1as Earth's mass is 80 times moon's.and,D:d = 4:1as their diameters are in the given ration in the question.

by devidingequation 1 by 2,(1)/(2)

g/g ' = [4GM/D2]/[4Gm/d2]= [M/D2]/[m/d2]= [M:m]*[d2:D2]= ​[M:m]/[D:d]280/1]/[4/1]2= (80)/(16)= 5

Now,we have,g:g ' = 5:1so,g ' = g/5= 9.81/5= 1.9802≈1.98 m/s2

same with mine .okaay

Given distance of far point (D) = 2m

Let f be the focal length of eye lens.

Image distance (distance between eye lens and retina ) for our human eye is always constant and is about 2.5 cm.This is due to the action of ciliary muscles.

Applying lens formula, we get f = -D = -2 cm

but, the power of a lens is reciprocal of focal length.hence. Power = 1/f (f in meters)= 1/-2= - 0.5 dioptre.

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For this dot product should be 0.

=> P*Q = a*a -2a-3 = 0

=> a²-2a-3 = 0=> a²-3a+a-3 = 0=> a(a-3) + 1(a-3) = 0=> (a-3)(a+1) = 0=> a = 3 , -1

since B×A will be a vector that will be _|_ to both A and B

now for product of _|_ vector with A will always be 0 , because angle will be 90° and cos(90°) =0