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प्रश्न
The phenomena involved in the reflection of radiowaves by ionosphere is similar to ______.
पर्याय
reflection of light by a plane mirror.
total internal reflection of light in air during a mirage.
dispersion of light by water molecules during the formation of a rainbow.
scattering of light by the particles of air.
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उत्तर
The phenomena involved in the reflection of radiowaves by ionosphere is similar to total internal reflection of light in air during a mirage.
Explanation:
Radio waves are reflected by a layer of the atmosphere called the Ionosphere, so they can reach distant parts of the Earth. The reflection of radio waves by ionosphere is due to total internal reflection. It is the same as total internal reflection of light in the air during a mirage, i.e., angle of incidence is greater than critical angle.
Important point: The ionized part of the Earth’s atmosphere is known as the ionosphere. Ultraviolet light from the sun collides with atoms in this region knocking electrons loose. The creates ions or atoms with missing electrons. This is what gives the Ionosphere its name- and it is the free electrons that cause the reflection and absorption of ratio waves.
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संबंधित प्रश्न
Write the necessary conditions for the phenomenon of total internal reflection to
occur ?
Write the relation between the refractive index and critical angle for a given pair of optical media?
One day Chetan’s mother developed a severe stomach ache all of a sudden. She was rushed to the doctor who suggested for an immediate endoscopy test and gave an estimate of expenditure for the same. Chetan immediately contacted his class teacher and shared the information with her. The class teacher arranged for the money and rushed to the hospital. On realizing that Chetan belonged to a below average income group family, even the doctor offered concession for the test fee. The test was conducted successfully.
Answer the following questions based on the above information:
(a) Which principle in optics is made use of in endoscopy?
(b) Briefly explain the values reflected in the action taken by the teacher.
(c) In what way do you appreciate the response of the doctor on the given situation?
Express the refractive index μ of a medium in terms of the angle of incidence i in air and the angle of refraction r in a denser medium.
State one factor on which a critical angle for a given pair of media depends. The critical angle for the glass-air interface is 45° for the yellow light. Will it be equal to, less than or greater than 45° for (i) red light, (ii) blue light?
A ray of light is incident as a normal ray on the surface of separation of two different mediums. What is the value of the angle of incidence in this case?
Explain ‘mirage’ as an illustration of refraction.
Describe the construction and working of an optical fibre.
Observe the given figure and write appropriate phenomenon of light in the box.
Critical angle of light passing from glass to air is maximum for ____________.
The critical angle is defined as the angle of incidence at which the total internal reflection starts to occur.
The angle of incidence at which the angle of refraction is Q£ is called the critical angle.
What are the conditions to achieve total internal reflection?
What is a mirage? How does it occur?
Write any two uses of total internal reflection.
What are the examples of total internal reflection in nature?
A ray of light incident at an angle θ on a refracting face of a prism emerges from the other face normally. If the angle of the prism is 5° and the prism is made of a material of refractive index 1.5, the angle of incidence is ______.
A rectangular block of glass ABCD has a refractive index 1.6. A pin is placed midway on the face AB (Figure). When observed from the face AD, the pin shall ______.
- appear to be near A.
- appear to be near D.
- appear to be at the centre of AD.
- not be seen at all.
State two differences between normal reflection and total internal reflection.
