NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes (EX 15.4) Exercise 15.4

Q.1

$\begin{array}{l}\text{A bulb is kept burning just right above the following solids.}\\ \text{Name the shape of the shadows obtained in each case.}\\ \text{Attempt to give a rough sketch of the shadow.(You may}\\ \text{try to experiment first and then answer these questions).}\end{array}$

Ans

\begin{array}{l}\text{The shapes of the shadows of these figures will be as follows:}\\ \text{(i) A ball}\end{array}

\text{The shape of the shadow of a ball will be a circle}\text{.} \text{(ii) A cylindrical pipe}

\text{The shape of the shadow of a cylindrical pipe will be a rectangle} \text{.}

\text{(iii) A book}

\text{The shape of the shadow of a book will be a rectangle}\text{.}

Q.2

$\begin{array}{l}\text{Here are the shadows of some 3-D objects, when seen}\\ \text{under the lamp of an over head projector. Identify the}\\ \text{solid}\left(\text{s}\right)\text{that match each shadow. (There may be}\\ \text{multiple answers for these!).}\end{array}$

Ans

\begin{array}{l}\text{The given shadows can be obtained in case of the following}\\ \text{objects}\text{.}\\ \text{(i) Compact disk (Sphere)}\\ \text{(ii) A}\text{}\text{dice (Cube)}\\ \text{(iii) Triangular pyramid (Cone)}\\ \text{(iv) Note Book (Cuboid)}\end{array}

Q.3

$\begin{array}{l}\text{Examine if the following are true statements:}\\ \left(\text{i}\right)\text{The cube can cast a shadow in the shape of a rectangle.}\\ \left(\text{ii}\right)\text{The cube can cast a shadow in the shape of a hexagon.}\end{array}$

Ans

\begin{array}{l}\text{A cube can cast shadow only in the shape of a square}\text{.}\\ \text{Therefore, any other shapes are not possible}\text{.}\\ \text{So,}\\ \text{(i) False}\\ \text{(ii) False}\end{array}