**1.** (a) Define strain.

(b) A rubber band is stretched to twice its original length. Calculate the strain on the rubber band.

**Correct Option: **

(a) Strain is the ratio of the original length of an object.

(b) Strain = c/lo= 2lo -lo/lo = 1

**2.** State three materials used for making optical fibres

**Brief Explanation:**

Materials for making optical fibre are Glass, Polycarbonate, Teflon sheath, Silica, quartz, Silicon, Sapphire. Feromagnetic

**3.** Name three classes of magnetic materials.

**Brief Explanation:**

Three classes of magnetic materials are

(i) Diamagnetic

(ii) Paramagnetic

(iii) Feromagnetic

**4. **(a) What is an intrinsic semiconductor?

(b) Distinguish between the p-type and n-type semi-conductors.

**Brief Explanation:**

(a) An intrinsic semiconductor contains equal number of free electrons and holes.

(b)

p— TYPE | n – TYPE | |

i | The majority carrier of electricity is holes. | The majority carrier of electricity is electron. |

ii | Carries a net positive charge | Carries a net negative charge |

iii | The impurity is trivalent | The impurity is pentavalent. |

**5.**A missile is projected so as to attain its maximum range. Calculate the maximum height attained if the initial velocity of projection is 200 ms−¹. [g = 10ms−²]

**Brief Explanation:**

**6. **A black body radiates maximum energy when its surface temperature T and the corresponding wavelength λmax are related by the equation $\lambda $max T = constant. Given the values of the constant and surface temperature as 2.9 x 10−3 mK and 57°C respectively; Calculate the frequency of the energy radiated.

**Brief Explanation:**

\(\lambda\) max = \(\frac{2.9 \times 10^{-3}}{330}\) = 8.8 x 10\(^{-6}\)m

v = f\(\lambda\) or f = \(\frac{v}{\lambda}\)

where v = velocity of light = 3.0 x10\(^{-8}\) m/s

\(\lambda\) = 8.8 x 10\(^{-6}\)

f = \(\frac{v}{\lambda}\)

= \(\frac{3.0 \times 10^8}{8.8 \times 10^{-6}}\)

= 3.4 x 10\(^{13}\) Hz

**7. **a) What does the acronym LASER stand for?

b) What is a laser?

**Brief Explanation:**

(a) LASER – Light Amplification by Stimulated Emission of Radiation.

(b) A laser is a device that generates an intense beam of coherent monochromatic light.

**8. **(a) Define uniform acceleration.

(b) Forces act on a car in motion. List the

(i) horizontal forces and their directions;

(ii) vertical forces and their directions

(c) A car starts from rest and accelerate uniformly for 20s to attain a speed of 25 ms−1. It maintains this speed for 30s before decelerating uniformly to rest. The total time for the journey is 60s.

(i) Sketch a velocity-tune graph for the motion.

(ii) Use the graph to determine the (α$\alpha $) total distance travelled by the car ($\beta $) deceleration of the car.

The figure here illustrates force-extension graph for a stretched spiral spring. Determine the work done on the spring.

**Brief Explanation:**

(a) Uniform acceleration is the constant time rate of increase in velocity.

(b) (i) Horizontal Force;

Forward force – Thrust

backward force – Frictional force

(ii) Vertical Force

Upward force – Normal reaction.

Downward force – Weight of the car.

(c)

(ii) (λ) Total distance

= Area of trapezium OABC

= 1/2[AB + OC] AD

= 1/2[60+30] x 25

=1125m

(β) Deceleration = slope of BC

BE/CE=25/10

= 25m/s2

(d) Work done = 1/2Fe

= 1/2 x 12 x 0.5/100J

= 0.03J