Backscattered electron detector of a scanning electron microscope is used to
Show Hint
- study surface topography of the sample
- quantify surface roughness
- measure atomic number
- contrast areas with different chemical compositions
The Correct Option is D
Solution and Explanation
Step 1: Understanding Backscattered Electrons (BSE)
Backscattered electrons are high-energy electrons that are reflected after interacting with atomic nuclei. Their intensity increases with atomic number, forming brightness contrast in images.
Step 2: Why BSE Gives Composition Contrast
Since heavier elements reflect more electrons, BSE images show bright–dark variations based on material composition. Hence, BSE detectors are ideal for distinguishing regions with different chemical compositions.
Step 3: Eliminating Incorrect Options
- Surface topography and roughness are mainly analyzed using secondary electrons, not BSE.
- BSE does not directly measure atomic number, it only gives contrast based on it.
Top Questions on Ultrasound and its application
- Which of the following statement(s) about ultrasound waves is/are true?
- GATE BM - 2025
- Medical Imaging Systems
- Ultrasound and its application
- If a circular ultrasound transducer of radius a = 8 mm operating at a central frequency of 1 MHz has a pressure beam pattern in a medium as given below :
\(P(r,0) \propto\sin\frac{ka^2}{4r}\)
Here, k is the wave number, r is the axial distance from the center of aperture. The speed of sound in the medium is 1600 ms-1.
The reduction in intensity between r = 8 cm and r = 16 cm is _______ dB. Give your answer as a positive quantity rounded off to two decimal places.- GATE BM - 2024
- Medical Imaging Systems
- Ultrasound and its application
- A Doppler ultrasound transducer operating at 5 MHz gave maximum output frequency shift of 3 kHz. The velocity of sound in blood is 1500 m/s. If the probe was held at an angle of 45° to the direction of blood flow, the maximum velocity of blood flow through the artery is _______ m/s. (Give your answer rounded off to two decimal places.)
- GATE BM - 2024
- Medical Imaging Systems
- Ultrasound and its application
- The 1stgeneration (1G) CT scanner uses a point X-ray source and a detector. The source-detector assembly can move linearly at a speed of 0.5 m.s\(^{-1}\) and it takes 0.5 s for source-detector assembly to rotate one angular increment, regardless of the angle. This scanner is expected to collect 360 projections over 180° of span. The field of view used for data collection has a diameter of 0.5 m. The scan time required is _____ s.
- GATE BM - 2022
- Medical Imaging Systems
- Ultrasound and its application
- A PZT crystal of thickness 1 mm and wave velocity 4000 m/s is emitting a longitudinal pressure wave, which is incident on a blood vessel at an angle of 30°. The Doppler shift in the ultrasound wave for a blood flow of 10 cm/s and wave velocity in the soft tissue of 1540 m/s is \(\underline{\hspace{2cm}}\) Hz.
- GATE BM - 2021
- Medical Imaging Systems
- Ultrasound and its application
Questions Asked in GATE BM exam
A Wheatstone bridge is used to measure strain as shown in the figure below.
Initially, the bridge was balanced. When a strain is applied to the resistor \( R_{{strain}} \), along its length, the output voltage \( V_{{out}} \) is 10 mV. If \( R_{{strain}} \) is a cylindrical resistor of length \( l \) and cross-sectional area \( A \), the magnitude of the applied strain is _______.
(rounded off to two decimal places)
- GATE BM - 2025
- Decay processes
An ideal, massless spring with spring constant 1 N/m (upper panel of the given figure) is cut into 5 equal parts. If two of these parts are connected in parallel (lower panel of the given figure), what is the resultant spring constant in N/m? (rounded off to the nearest integer)
- GATE BM - 2025
- Phase Shift Keying (PSK)
The plot of \( \log_{10} ({BMR}) \) as a function of \( \log_{10} (M) \) is a straight line with slope 0.75, where \( M \) is the mass of the person and BMR is the Basal Metabolic Rate. If a child with \( M = 10 \, {kg} \) has a BMR = 600 kcal/day, the BMR for an adult with \( M = 100 \, {kg} \) is _______ kcal/day. (rounded off to the nearest integer)
- GATE BM - 2025
- Positron Emission Tomography
For the RLC circuit shown below, the root mean square current \( I_{{rms}} \) at the resonance frequency is _______amperes. (rounded off to the nearest integer)
\[ V_{{rms}} = 240 \, {V}, \quad R = 60 \, \Omega, \quad L = 10 \, {mH}, \quad C = 8 \, \mu {F} \]- GATE BM - 2025
- Electrical Circuits
The frequency of the oscillator circuit shown in the figure below is _______(in kHz, rounded off to two decimal places).
Given: \( R = 1 \, k\Omega; R_1 = 2 \, k\Omega; R_2 = 6 \, k\Omega; C = 0.1 \, \mu F \)- GATE BM - 2025
- Phase Shift Keying (PSK)