Test on Microscopes: light, SEM and TEM

Question 1: Electrons used in electron microscopes have significantly longer wavelengths than visible light.

A. Yes

B. No

Explanation: Electron microscopes use a beam of electrons, which have significantly shorter wavelengths than visible light. This shorter wavelength allows for a much higher resolution compared to light microscopes.

Question 2: Transmission Electron Microscopy (TEM) is primarily used to visualize the surface topography of a virus, showing its overall 3D shape.

A. Yes

B. No

Explanation: TEM is essential for visualizing viruses, revealing their detailed internal morphology, including the capsid, nucleic acid core, and associated structures like envelopes or tail fibers. It does not primarily show surface topography or overall 3D shape, which is more characteristic of SEM for larger viral particles or clusters.

Question 3: According to the study materials, which aspect of a mitochondrion can be visualized using a Scanning Electron Microscope (SEM)?

A. The outer surface of the mitochondrion

B. The double membrane structure with cristae

C. Ribosomes and mitochondrial DNA within the matrix

D. Detailed internal structures crucial for understanding its function

Explanation: The study materials state that 'SEM can show the outer surface of a mitochondrion, but its internal structure is not visible.' Therefore, only the outer surface can be visualized by SEM. The other options describe internal structures that are explicitly mentioned as not visible or are best seen with TEM.

Question 4: According to the provided study materials, which factors primarily govern the resolution limit of a light microscope?

A. The wavelength of light used

B. The magnification of the eyepiece lens

C. The numerical aperture (NA) of the objective lens

D. The size of the sample being observed

Explanation: The study materials state that the resolution limit of a light microscope is 'governed by the wavelength of light and the numerical aperture (NA) of the objective lens.' The formula d = λ / (2 · NA) further clarifies this, where λ is the wavelength of light and NA is the numerical aperture. While eyepiece magnification contributes to total magnification, it does not govern the resolution limit. The size of the sample does not govern the microscope's inherent resolution limit.

Question 5: The objective lens in a Transmission Electron Microscope forms the primary magnified image.

A. Yes

B. No

Explanation: According to the study materials, specifically the 'Electron Path in TEM' section, the Objective Lens is responsible for forming the primary magnified image.