NEET (2024 Updated)-National Eligibility cum Entrance Test (Medical) Chemistry Coaching Programs
📹 Video Course 2024 (8 Lectures [4 Hrs : 33 Mins]): Offline Support
Click Here to View & Get Complete Material
Rs. 100.00
1 Month Validity (Multiple Devices)
⏳ 🎯 Online Tests (5 Tests [50 Questions Each]): NTA Pattern, Analytics & Explanations
Click Here to View & Get Complete Material
Rs. 500.00
3 Year Validity (Multiple Devices)
🎓 Study Material (159 Notes): 2024-2025 Syllabus
Click Here to View & Get Complete Material
Rs. 350.00
3 Year Validity (Multiple Devices)
🎯 3111 MCQs (& PYQs) with Full Explanations (2024-2025 Exam)
Click Here to View & Get Complete Material
Rs. 650.00
3 Year Validity (Multiple Devices)
NCERT Physics Class 12 Exemplar Ch 15 Communication Systems Part 3
Q 23 If the whole earth is to be connected by LOS communication using space waves (no restriction of antenna size or tower height) , what is the minimum number of antennas required? Calculate the tower height of these antennas in terms of earth՚s radius?
Ans:
Since space wave frequency is used, , hence only tower height is taken to consideration.
In three dimensions, 6 antenna towers of would do.
Q 24 The maximum frequency for reflection of sky waves from a certain layer of the ionosphere is found to be , where the maximum electron density at that layer of the ionosphere is. On a certain day it is observed that signals of frequencies higher than 5 MHz are not received by reflection from the layer of the ionosphere while signals of frequencies higher than 8 MHz are not received by reflection from the layer of the inonosphere. Estimate the maximum electron densities of the and layers on that day.
Ans:
For layer
For layer
Q 25 On radiating (sending out) an AM modulated signal, the total radiated power is due to energy carried by . Suggest ways to minimize cost of radiation without compromising on information.
Ans:
- Of only contains information.
- Hence cost can be reduced by transmitting both