Home
Class 12
PHYSICS
Assertion: The ionosphere layer acts as ...

Assertion: The ionosphere layer acts as a reflector for all range of frequencies.
Reason: Ionosphere does not allow electromagnetic wav e to penetrate and escape.

A

Both A and R are correct and R is correct explaination of A

B

A is correct but R is wrong

C

A is wrong but R is correct

D

Both A and R are wrong

Text Solution

Verified by Experts

The correct Answer is:
D
The ionosphere layer acts as a reflector for a certain rang of frequencies is 3 to 30 MHz. Electromagnetic waves of frequencies higher than 30 MHz penetrate the ionosphere and escape.
Promotional Banner

Topper's Solved these Questions

  • COMMUNITCATION SYSTEMS

    NCERT FINGERTIPS ENGLISH|Exercise Introduction|2 Videos

  • COMMUNITCATION SYSTEMS

    NCERT FINGERTIPS ENGLISH|Exercise Elements Of A Communication System|4 Videos

  • COMMUNITCATION SYSTEMS

    NCERT FINGERTIPS ENGLISH|Exercise NCERT|9 Videos

  • ATOMS

    NCERT FINGERTIPS ENGLISH|Exercise Assertion And Reason|15 Videos

  • CURRENT ELECTRICITY

    NCERT FINGERTIPS ENGLISH|Exercise Assertion And Reason|15 Videos

Similar Questions

Explore conceptually related problems

Assertion: In ionospheric reflection, phase change does not occurs with the light wave. Reason: The ionosphere reflection is similar to the tatol internal reflection is similar to the total internal reflection in miral.

Assertion : If you burn a plant , its nitrogen component is given off as ammonia and other gases . Reason : Hydroponics does not allow plants to grow well if they are supplied with all the mineral nutrients they need.

Assertion : Static crashes are heard on radio, when lightning flash occurs in the sky. Reason : Electromagnetic waves having frequency of radiowave range, interfere with radiowaves.

Assertion : All types of electromagnetic radiation travel with the same E velocity. Reason : Electromagnetic radiations possess a dual nature, i.e., they behave both as particle andzas wave.

Write true (T) or false (F) (a) Epithelial tissue is protective tissue in animal body. (b) The lining of blood vessels, lung alveoli and kidney tubules are all made up of epithelial tissue. (c) Epithelial cells have a lot of intercellular spaces. (d) Epithelial layer is permeable layer. (e) Epithelial layer does not allow regulation of materials between body and external environment

When electromagnetic waves enter the ionised layer of ionosphere , then the relative permittivity i.e., dielectric constant of the ionised layer

The force of interaction between the molecules of same substance is called cohesive force hile force of interaction between molecules of different substances is called adhesive force . Both the forces are attracive and have a range of about 10 A . If we consider a molecule . A well inside a liquid we find that it is equally attracted by the surrounding molecules in all the directions ( with a sphere of radius 10 Å ) and so it does not experience any resultant force . On or near the surface of a liquid , the molecules do not exist on the free side and so a molecule ( say B ) experiences a resultant force vertically downwards into the liquid . For this reason , the molecules of the surface have a tendency to go into the liquid . Thus , the surface tends to contract and gives rise to surface tension . As surface molecules like B experience a net downward force of cohension and have tendency to go down , so in increasing the area of the surface more molecules are to be shifted to the surface from inside . Thus , more mechnical work will have to be done against the net downward force of cohension . This work is stored by the molecules in the surfaces as potential energy called free surface energy . Furthermore , molcules like P , in contact with the liquid will stick to the solid surface , i.e will meet it if the force of adhesion A is greater than net force of cohension C . The liquid will not the solid surface if C gt A Also , molecules like Q at the surface in contact with the solid will experience a net force of cohension C_(R) . If adhesion A is greater then cohension C_(R) , the resultant force will be F . As the liquid can't support tangential force , F must be perpendicular to the surface of the liquid . So , the menisus will be concave and the angle of contact will be acute ( gt 90^(@)) . However , if adhesion is lesser than cohension , the resultant force F will be directed into the liquid and so the menisus ( which is perpendicular to F as liquid support tangential force ) will be convex and the angle of contact will be obtuse ( gt 90^(@)) A liquid particle B , which is present in the vicinity particle A can exert a force on A if the distance of B from A is

The force of interaction between the molecules of same substance is called cohesive force hile force of interaction between molecules of different substances is called adhesive force . Both the forces are attracive and have a range of about 10 A . If we consider a molecule . A well inside a liquid we find that it is equally attracted by the surrounding molecules in all the dirctions ( with a sphere of radius 10 Å ) and so it does not experience any resultant force . On or near the surface of a liquid , the molecules do not exist on the free side and so a molecule ( say B ) experiences a resultant force vertically downwards into the liquid . For this reason , the molecules of the surface have a tendency to go into the liquid . Thus , the surface tends to contract and gives rise to surface tension . As surface molecules like B experience a net downward force of cohension and have tendency to go down , so in increasing the area of the surface more molecules are to be shifted to the surface from inside . Thus , more mechnical work will have to be done against the net downward force of cohension . This work is stored by the molecules in the surfaces as potential energy called free surface energy . Furthermore , molcules like P , in contact with the liquid will stick to the solid surface , i.e will meet it if the force of adhesion A is greater than net force of cohension C . The liquid will not the solid surface if C gt A Also , molecules like Q at the surface in contact with the solid will experience a net force of cohension C_(R) . If adhesion A is greater then cohension C_(R) , the resultant force will be F . As the liquid can't support tangential force , F must be perpendicular to the surface of the liquid . So , the menisus will be concave and the angle of contact will be acute ( gt 90^(@)) . However , if adhesion is lesser than cohension , the resultant force F will be directed into the liquid and so the menisus ( which is perpendicular to F as liquid support tangential force ) will be convex and the angle of contact will be obtuse ( gt 90^(@)) The free suface energy , stored in the surface is because of work done