Class 12 Computer Science Ch 11 Data Communication NCERT Book Exercise Solution

NCERT Book Exercise Solution Question and Answer

Ch. 11 – Data Communication

7. List out the advantages and disadvantages of optical fiber cable.

Answer: Advantages of Optical Fiber

(i) Higher bandwidth (higher data transfer) compare to twisted pair and coaxial cable.

(ii) Faster data transmission speed compared to other guided media.

(iii) Negligible data loss or information.

(iv) Secure transmission media, difficult to tap.

Disadvantages of Optical Fiber

(i) Most expensive, compared to other guided media.

(ii) Difficult installation and modification

(iii) More vulnerable/fragile to damage compared to copper wires.

(iv) Special device and expert require to connect or join.

8. What is the range of frequency for radio waves?

Answer: Frequency of Radio Waves : 3 KHz to 1 GHz

Note:

Frequency of Micro Waves : 1 GHz to 300 GHz

Frequency of Infrared Waves : 300 GHz to 400 THz

Frequency of Light Waves : 400 THz to 900 THz

Frequency of Bluetooth : 2.4 GHz

9. 18 Gbps is equal to how many Bits per second?

Answer: 18 Gbps = 18 x 1000 Mbps = 18,000 Mbps

18,000 Mbps x 1000 Kbps = 1,80,00,000 Kbps

1,80,00,000 Kbps x 1000 bps = 18,00,00,00,000 bps

10. HTTP stands for?

Answer: Hypertext Transfer Protocol

11. Write short note on the following: a) HTTP b) Bandwidth c) Bluetooth d) DNS e) Data transfer rate

Answer:

a) HTTP :

HTTP stands for HyperText Transfer Protocol. It is the primary protocol used to access the World Wide Web.

HTTP is a request-response (also called client server) protocol that runs over TCP. The common use of HTTP is between a web browser (client) and a web server (server). HTTP facilitates access of hypertext from the World Wide Web by defining how information are formatted and transmitted, and how the Web servers and browsers should respond to various commands.

b) Bandwidth :

Bandwidth of a channel is the range of frequencies available for transmission of data through that channel. Higher the bandwidth, higher the data transfer rate.

Normally, bandwidth is the difference of maximum and minimum frequency contained in the composite signals. Bandwidth is measured in Hertz (Hz).

c) Bluetooth :

Bluetooth is a short-range wireless technology that can be used to connect mobile-phones, mouse, headphones, keyboards, computers, etc. wirelessly over a short distance.

All these bluetooth-enabled devices have a low cost transceiver chip. This chip uses the unlicensed frequency band of 2.4 GHz to transmit and receive data. These devices can send data within a range of 10 meters with a speed of 1 – 2 Mbps.

d) DNS :

Conversion of the domain name of each web server to its corresponding IP address is called domain name resolution. It is done through a server called
DNS server.

e) Data transfer rate :

Data transfer rate is the number of bits transmitted between source and destination in one second. It is also known as bit rate. It is measured in terms of bits per second (bps).

The higher units for data transfer rates are:
1 Kbps = 210 bps = 1024 bps
1 Mbps = 220 bps = 1024 Kbps
1 Gbps = 230 bps = 1024 Mbps
1 Tbps = 240 bps = 1024 Gbps

12. What is protocol in data communication? Explain with an example.

Answer: In communication, Protocol is a set of standard rules that the communicating parties — the sender, the receiver, and all other intermediate devices need to follow.

Various data communication protocols are :

HTTP : HyperText Transfer Protocol,

FTP : File Transfer Protocol,

TCP/IP : Transmission Control Protocol Internet Protocol,

SMTP : Simple Mail Transfer Protocol,

POP : Post Office Protocol,

PPP : Point to Point Protocol

13. A composite signal contains frequencies between 500 MHz and 1GHz. What is the bandwidth of a signal?

Answer: Bandwidth is the difference of maximum and
minimum frequency contained in the composite signals. Bandwidth is measured in Hertz (Hz).

Bandwidth = Higher Frequency – Lower Frequency

= 1000 MHz – 500 Mhz

= 500 MHz = 5,00,000 KHz = 50,00,00,000 Hz