Answer: They are put in front for defense so so they can block the opponents from getting the ball
Explanation:
Answer:
Explanation:
b ) First is concave lens with focal length f₁ = - 12 cm .
object distance u = - 20 cm .
Lens formula
1 / v - 1 / u = 1 / f
1 / v + 1 / 20 = -1 / 12
1 / v = - 1 / 20 -1 / 12
= - .05 - .08333
= - .13333
v = - 1 / .13333
= - 7.5 cm
first image is formed before the first lens on the side of object.
This will become object for second lens
distance from second lens = 7.5 + 9 = 16.5 cm
c )
For second lens
object distance u = - 16.5 cm
focal length f₂ = + 12 cm ( lens is convex )
image distance = v
lens formula ,
1 / v - 1 / u = 1 / f₂
1 / v + 1 / 16.5 = 1 / 12
1 / v = 1 / 12 - 1 / 16.5
= .08333- .0606
= .02273
v = 1 / .02273
= 44 cm ( approx )
It will be formed on the other side of convex lens
distance from first lens
= 44 + 9 = 53 cm .
magnification by first lens = v / u
= -7.5 / -20 = .375 .
magnification by second lens = v / u
= 44 / - 16.5
= - 2.67
d )
total magnification
= .375 x - 2.67
= - 1.00125
height of final image
= 2.50 mm x 1.00125
= 2.503mm
e )
The final image will be inverted with respect to object because total magnification is negative .
Answer:
Explanation:
Assuming uniform spread of sound with no significant reflections or absorption. We know that sound intensity varies 
where r is the distance
Since intensity is given then when at 3 m
Since we have the constant then at 4m
Intensity, 
Using the given formula with v0=56 ft/s and h=40 ft
h = -16t2 + v0t
40 = -16t2 + 56t
16t2 - 56t + 40 = 0
Solving the quadratic equation:
t= (-b+/-(b^2-4ac)^1/2)/2a = (56+/-((-56)^2-4*16*40)^1/2)/2*16 = (56 +/- 24) / 32
We have two possible solutions
t1 = (56+24)/32 = 2.5
t2 = (56-24)/32 = 1
So initially the ball reach a height of 40 ft in 1 second.
Answer:
Explanation:
An atom is constructed of three different particles known as electrons, protons and neutrons.
These particles have different mass and charges and are responsible for various characters than an atom posses.
An electron has a negative charge, a proton has positive charge and charge of neutron is neutral. Equal number of electrons and protons are present in an atom that make it electrically neutral but different conditions can occur if we remove these particles from an atom.
1 : Model of an ionized atom - an ionized atom is one which has some net charge on this. It can be either a positive charge or a negative charge.
If we need to sketch the model of an ionized atom then one should either keep the number of electrons less or proton.
2: Model of radioactive atom : A radioactive atom is one an unstable atom and has access of energy in its center. It can be caused by adding either neutrons or protons.
