Question

Assertion :  Television signals are received through sky-wave propagation.

Reason    : The ionosphere reflects electromagnetic waves of frequencies greater than a certain critical frequency.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If the assertion and reason both are false.

Answer

(d) If the assertion and reason both are false.

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Similar questions

A drop of   water carries   charge. What electric field should be applied to balance its weight (assume  

(a) 10 V/m upward

(b) 10 V/m downward

(c) 0.1 V/m downward

(d) 0.1 V/m upward

Which of the following isotopes is used for the treatment of cancer

(a)  

(b)  

(c)    

(d)  

Two strings A and B, made of same material, are stretched by same tension. The radius of string A is double of the radius of B. A transverse wave travels on A with speed $\nu_\text{A}$ and on B with speed $\nu_\text{B}.$ The ratio $\frac{\nu_\text{A}}{\nu_\text{B}}$ is:

  1. $\frac{1}{2}$

  2. $2$

  3. $\frac{1}{4}$

  4. $4.$

In one average-life:

Consider the following statements A and B and identify the correct choice of the given answers

(A) A zener diode is always connected in reverse bias

(B) The potential barrier of a PN junction lies between 0.1 to 0.3 V approximately

(a) A and B are correct

(b) A and B are wrong

(c) A is correct but B is wrong

(d) A is wrong but B is correct

Which of the following is not the property of a cathode ray

(a) It casts shadow

(b) It produces heating effect

(c) It produces flurosence

(d) It does not deflect in electric field

Select the correct alternative, The angle between the normal and refracted ray is called:

Material A has critical angle   and material B has critical angle . Then which of the following is true

(i) Light can be totally internally reflected when it passes from B to A

(ii) Light can be totally internally reflected when it passes from A to B

(iii) Critical angle for total internal reflection is  

(iv) Critical angle between A and B is

(a) (i) and (iii)

(b) (i) and (iv)

(c) (ii) and (iii)

(d) (ii) and (iv)

A laser beam can be focussed on an area equal to the square of its wavelength A He-Ne laser radiates energy at the rate of 1mW and its wavelength is 632.8 nm. The intensity of focussed beam will be

(a) 1.5  

(b) 2.5  

(c) 3.5  

(d) None of these

A particle is kept at rest at a distance R (earth's radius) above the earth's surface. The minimum speed with which it should be projected so that it does not return is:

  1. $\sqrt{\frac{\text{GM}}{4\text{R}}}$

  2. $\sqrt{\frac{\text{RM}}{2\text{R}}}$

  3. $\sqrt{\frac{\text{GM}}{\text{R}}}$

  4. $\sqrt{\frac{2\text{GM}}{\text{R}}}$