CBSE Class 11 Geography Chapter 7: Introduction to Remote Sensing NCERT Solutions

Reviewed by NCERT Help Editorial Team · Updated on 29 Jul 2026

NCERT Solutions PDF Class 11 PDF

This chapter provides a foundational understanding of Remote Sensing for Class 11 Geography students following the CBSE curriculum. It delves into the fundamental principles of remote sensing, including the evolution of different remote sensing techniques and the various regions of the electromagnetic spectrum utilized. The solutions explain the functioning of different types of scanners, such as whiskbroom and pushbroom scanners, and highlight their differences. Additionally, it touches upon the application of remote sensing in observing changes in vegetation, using the Himalayas as an example. These solutions are designed to clarify complex concepts and aid students in their exam preparation by offering detailed explanations and step-by-step answers to the NCERT textbook questions.

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Quick info

Board	CBSE
Class	Class 11
Subject	Practical Work in Geography
Session	2026
Language	English
Type	NCERT Solutions
Chapter	Chapter 7

Chapter summary

Chapter 7, 'Introduction to Remote Sensing,' covers the basic concepts of acquiring information about an object or phenomenon without making physical contact. The NCERT Solutions explain the historical evolution of remote sensing methods, the electromagnetic spectrum's role, and the distinct operational mechanisms of whiskbroom and pushbroom scanners. It also includes practical applications like observing vegetation changes in the Himalayas. This chapter focuses on understanding the core principles and technologies behind remote sensing.

Learning outcomes

Understand the evolution of remote sensing techniques.
Identify the regions of the electromagnetic spectrum used in satellite remote sensing.
Differentiate between IRS and INSAT satellite series.
Explain the functioning of whiskbroom and pushbroom scanners.
Analyze changes in vegetation using remote sensing imagery.

Topics covered

Paper topics

Introduction to Remote Sensing
Evolution of Remote Sensing Techniques
Electromagnetic Spectrum in Remote Sensing
IRS Satellite Series
INSAT Satellite Series
Whiskbroom Scanner
Pushbroom Scanner
Visual Interpretation Techniques
Application in Vegetation Analysis
Comparison of Scanners

Important topics

Evolution of Remote Sensing
Whiskbroom vs. Pushbroom Scanners
Electromagnetic Spectrum Usage
IRS vs. INSAT Satellites
Vegetation Change Detection

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Questions and Solutions

Question 1 (i)

Choose the right answer from the four alternatives given below: Remote sensing of objects can be done through various means such as remote sensors, human eyes, and photographic systems. Which of the following represents the true order of their evolution?

(a) ABC

(b) BCA

(d) None of the above

Solution: The correct order of the evolution of remote sensing techniques starts with the most basic form and progresses to more advanced methods. Initially, humans relied on their own vision (human eyes) to observe and understand their surroundings. This was followed by the development of photographic systems, which allowed for the capture and recording of images. Finally, sophisticated remote sensors were developed, enabling the collection of data across various parts of the electromagnetic spectrum without direct human observation. Therefore, the true evolutionary order is Human Eyes (B), Photographic System (C), and Remote Sensors (A). This corresponds to option (b) BCA.

Question 1 (ii)

Choose the right answer from the four alternatives given below: Which of the following regions of the Electromagnetic spectrum is not used in satellite remote sensing?

(a) Microwave region

(b) Infrared region

(d) Visible region

Solution: Satellite remote sensing relies on detecting electromagnetic radiation that interacts with the Earth's surface. The commonly used regions of the electromagnetic spectrum include the visible region (which our eyes can see), the infrared region (useful for detecting temperature and vegetation health), and the microwave region (which can penetrate clouds and is used for radar imaging). X-rays, however, are a form of high-energy radiation that is not typically used in standard satellite remote sensing due to their properties and the specialized equipment required to detect them, as well as their significant atmospheric absorption.

Question 1 (iii)

Choose the right answer from the four alternatives given below: Which of the following is not used in visual interpretation technique?

(a) Spatial arrangements of objects

(b) Frequency of tonal change on the image

(d) Digital image processing

Solution: Visual interpretation of remote sensing imagery involves analyzing images by eye, often with the aid of stereoscopes or magnifying lenses. Key elements used in this technique include the spatial arrangement of objects (their shape and pattern), their location relative to other objects (context), and their texture. The frequency of tonal change on an image relates to texture and pattern. Digital image processing, on the other hand, is a computational method that uses algorithms to analyze and manipulate image data, rather than direct human visual analysis of the image itself. Therefore, digital image processing is not a part of the visual interpretation technique.

Question 2 (i)

Answer the following questions in about 30 words: Why is remote sensing a better technique than other traditional methods?

Solution: Remote sensing is superior to traditional methods for collecting information about the Earth's surface because it allows for data acquisition without physical contact. It is more efficient for large areas, provides information on spatial distribution and object properties, and can monitor seasonal changes, overcoming the time-consuming and impractical nature of ground surveys for extensive projects.

Question 2 (ii)

Answer the following questions in about 30 words: Differentiate between IRS and INSAT series of satellites.

Solution: The IRS (Indian Remote Sensing) satellite series consists of satellites orbiting at lower altitudes (700-900 km) to provide detailed Earth observation and mapping services over India. In contrast, the INSAT (Indian National Satellite) series comprises multipurpose geostationary satellites orbiting at a much higher altitude (approximately 36,000 km) to facilitate telecommunications, broadcasting, meteorology, and search and rescue operations.

Question 2 (iii)

Answer the following questions in about 30 words: Describe in brief the functioning of a push broom scanner.

Solution: A push broom scanner functions using a linear array of multiple detectors. Each detector in the array is responsible for collecting reflected energy from a specific ground cell (pixel) as the satellite moves. The entire swath width is captured simultaneously by this array of detectors, providing an image without the need for a scanning mirror.

Question 3 (i)

Answer the following questions in about 125 words: Describe the operation of a whiskbroom scanner with the help of a diagram. Explain how it is different from a pushbroom scanner.

Solution: A whiskbroom scanner operates by using a mirror that sweeps across the sensor's field of view, perpendicular to the satellite's flight path. This mirror reflects incoming radiation from the Earth's surface into a single detector, which records the energy for one pixel at a time. The mirror's motion allows the detector to scan across a range of angles (typically 90° to 120°), capturing data from the visible to the middle infrared regions of the electromagnetic spectrum.

The primary difference between a whiskbroom scanner and a pushbroom scanner lies in their detector configuration and scanning mechanism. A whiskbroom scanner uses a single detector and a moving mirror to scan the scene pixel by pixel. In contrast, a pushbroom scanner employs a linear array of numerous detectors, where each detector corresponds to a specific spatial resolution element across the entire swath. This array captures the entire swath simultaneously, eliminating the need for a scanning mirror and providing a more efficient data acquisition process.

Question 3 (ii)

Answer the following questions in about 125 words: Identify and list the changes that can be observed in the vegetation of the Himalayas.

Solution: Remote sensing imagery, such as that from the IRS satellite, can reveal significant seasonal changes in the vegetation of the Himalayas and the Northern Indian Plains. For instance, comparing images taken in May and November can highlight differences in vegetation cover and type. In a May image, prominent red patches might indicate the presence of coniferous vegetation, which thrives in the mountainous regions. By November, additional red patches may appear, signifying the presence of deciduous vegetation, which sheds its leaves seasonally. Furthermore, lighter red colors in the November image could correspond to rabi crops, indicating agricultural activity during that period. These observations demonstrate how remote sensing aids in monitoring vegetation phenology and land use patterns throughout the year.

Common mistakes

Confusing the order of evolution of remote sensing methods.
Incorrectly identifying which parts of the electromagnetic spectrum are used.
Misunderstanding the operational differences between whiskbroom and pushbroom scanners.
Difficulty in applying remote sensing concepts to real-world examples like vegetation changes.

Revision tips

Focus on the chronological order of remote sensing evolution.
Memorize the key differences between whiskbroom and pushbroom scanners.
Understand the purpose and altitude differences between IRS and INSAT satellites.
Review the examples of vegetation analysis to grasp practical applications.

Practice MCQs

Q1. What is the correct chronological order for the evolution of remote sensing methods: human eyes, photographic system, remote sensors?

Q2. Which part of the electromagnetic spectrum is generally NOT used in satellite remote sensing?

Q3. What is a key characteristic of a push broom scanner?

Q4. How does a whiskbroom scanner differ from a pushbroom scanner?

Q5. What information can be inferred from IRS and INSAT satellite images of the Himalayas in May and November?

Frequently asked questions

What is remote sensing and why is it considered better than traditional methods?

Remote sensing is a technique to collect information about objects or phenomena on Earth's surface without physical contact. It's better than traditional methods because it's faster, more cost-effective for large areas, and can gather data on spatial distribution and seasonal changes efficiently, which is impractical with ground surveys.

What is the main difference between IRS and INSAT satellites?

IRS (Indian Remote Sensing) satellites orbit at a lower altitude (700-900 km) and are primarily used for detailed Earth observation and mapping over India. INSAT (Indian National Satellite) satellites are geostationary, orbiting at a much higher altitude (around 36,000 km), and are used for telecommunications, broadcasting, and meteorology.

How do whiskbroom and pushbroom scanners work differently?

A whiskbroom scanner uses a mirror to sweep across the scene, collecting data one pixel at a time with a single detector. A pushbroom scanner uses a linear array of many detectors, with each detector capturing data for a specific pixel across the entire swath simultaneously.

Which parts of the electromagnetic spectrum are relevant for satellite remote sensing?

Satellite remote sensing utilizes regions like the visible, infrared, and microwave regions of the electromagnetic spectrum to capture reflected or emitted energy from the Earth's surface.

Can remote sensing help observe changes in vegetation?

Yes, remote sensing is very effective for observing vegetation changes. By comparing satellite images taken at different times (e.g., May and November), changes in vegetation types, such as the presence of coniferous versus deciduous forests or different types of crops, can be identified.

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