2008 - JAMB Physics Past Questions and Answers - page 3
21
I. Total internal reflection of light.
II. Conservation of light energy.
III. Relative motion of the earth, sun and moon.
IV. Rectilinear propation of light.
which of the above is a phenomenon of total solar eclipse?
II. Conservation of light energy.
III. Relative motion of the earth, sun and moon.
IV. Rectilinear propation of light.
which of the above is a phenomenon of total solar eclipse?
A
I and IV only
B
II and IV only
C
I and III only
D
III and IV only
correct option: d
Due to rectilinear propagation of light we have ecslipse which occur as a result relative motion of the earth, sun and moon
Users' Answers & Comments22
An object of height 4cm is placed in front of a cuboid pinhole camera of size 6 cm. if the image formed is 2 cm high, how far is the object from the pinhole?
A
3.0 cm
B
8.0 cm
C
12.0 cm
D
16.0 cm
correct option: c
Magnification = (image height)/object height
= (lenght camera)/object distance from pin-hole
∴(2)/4 = (6)/X
X (4 x 6)/2 = 12 cm
Users' Answers & Comments= (lenght camera)/object distance from pin-hole
∴(2)/4 = (6)/X
X (4 x 6)/2 = 12 cm
23
An object of heights 5 cm is placed at 20 cm from a concave mirror of focal length 10 cm. the image height is?
A
20 cm
B
15 cm
C
10 cm
D
5 cm
correct option: d
(1)/V + (1)/U = (1)/f
(1)/V + (1)/20 = (1)/10
(1)/V = (1)/10 - (1)/20 = (2 -1)/20 = (1)/20
∴ V = 20 cm
mag = (image height)/object height = (v)/u
(X)/5 = (20)/50
X = 5 cm
Users' Answers & Comments(1)/V + (1)/20 = (1)/10
(1)/V = (1)/10 - (1)/20 = (2 -1)/20 = (1)/20
∴ V = 20 cm
mag = (image height)/object height = (v)/u
(X)/5 = (20)/50
X = 5 cm
24
Convex mirror are used as driving mirrors because images formed are?
A
erect, virtual and diminished
B
erect, real and diminished
C
erect, virtual and magnified
D
inverted virtual and diminished
correct option: a
Image formed by convex mirror is always erect, virtual and diminished
Users' Answers & Comments25
An object placed at the bottom of a well full of clear water appears closer to the surface due to?
A
diffraction
B
reflection
C
refraction
D
polarization
26
In the microscope, the eyepiece lens merely acts as?
A
an inverter
B
a refiner
C
a diminisher
D
a magnifier
27
An observer with normal eyes views an object with magnifying glass of focal length 5 cm. the angular magnification is?
[least distance of distinct vision D = 25 cm]
[least distance of distinct vision D = 25 cm]
A
-6
B
-5
C
5
D
6
correct option: a
Angular magnification, M = ((D)/F + 1) where D is least distance of distinct vision
∴ M = ((25)/5 + 1) = -6
Users' Answers & Comments∴ M = ((25)/5 + 1) = -6
28
A short chain is sometimes attached to the back of a petrol tanker to?
A
generate more friction
B
ensure the balancing of the tanker
C
caution the driver when overspeeding
D
conduct excess charges to the car
correct option: d
The friction between the tanker and air creates charges which the chain conducts to the ground.
Users' Answers & Comments29
An electric generator has e.m.f. of 240 V and an internal resistance of 1Ω if the current supplied by the generatoris 20A when the terminal voltage is 220 V, find the ratio of the power supplied to the power dissipated?
A
11:1
B
1:11
C
12:11
D
11:12
correct option: c
Power supplied = IE = 20 X 240 = 4800 W
Power dissipated = IV = 20 X 220 = 4400 W
(Power supplied)/Power dissipated = (4800 W)/4400 W
= (12)/11
Users' Answers & CommentsPower dissipated = IV = 20 X 220 = 4400 W
(Power supplied)/Power dissipated = (4800 W)/4400 W
= (12)/11
30
A generator is on daily use and in the process, ten 60 W and five 40 W tungsten bulbs are on for the same time interval. the energy consumed daily is?
A
0.96 kWh
B
19.2 kWh
C
9.60 kWh
D
19.20 kWh
correct option: b
Energy consumed = power x time
= (60 W x 10 + 40 W x 5) x 24 h
= (600 W + 200 W ) x 24 h
= 800 W x 24h = 19200 w h
= 19.2 kWh
Users' Answers & Comments= (60 W x 10 + 40 W x 5) x 24 h
= (600 W + 200 W ) x 24 h
= 800 W x 24h = 19200 w h
= 19.2 kWh