Answer:
a) Focal length of the lens is 8 cm which is a convex lens
b) 6 cm
c) The lens is a convex lens and produces a virtual image which is upright and two times larger than the object.
Explanation:
u = Object distance = 4 cm
v = Image distance = -8 cm
f = Focal length
Lens Equation

a) Focal length of the lens is 8 cm which is a convex lens
Magnification

b) Height of image is 2×3 = 6 cm
Since magnification is positive the image upright
c) The lens is a convex lens and produces a virtual image which is upright and two times larger than the object.
The correct answer to the question is- 
CALCULATION:
As per the question, the electric field generated by the source charge is 1236 N/C at a distance of 4 m.
Hence , electric field E = 1236 N/C.
The distance of the point R = 4m
We are asked to calculate the charge possessed by the source.
The electric field produced by a source charge of Q at a distance R is calculated as -
Electric field E = 
Here,
is called the absolute permittivity of the free space.
Hence, the charge of source is calculated as -
Q = 
= 
= 
= 
= 
Hence, the charge of source is 
Answer:
Explanation:
Two frequencies with magnitude 150 Hz and 750 Hz are given
For Pipe open at both sides
fundamental frequency is 150 Hz as it is smaller
frequency of pipe is given by

where L=length of Pipe
v=velocity of sound
for n=1
and f=750 is for n=5
thus there are three resonance frequencies for n=2,3 and 4
For Pipe closed at one end
frequency is given by

for n=0


for n=2

Thus there is one additional resonance corresponding to n=1 , between
and 
The acceleration is the change of speed/velocity over time. Thus to calculate this you do (V1-V2)/T or (11.2-9.6)/4 or 0.4 m/s^2