assets folder not reachable in cordova / ember.js project

i am developing an app for my windows phone 10, using ember.js and cordova. Why am I unable to display images - always getting the following error:

The app couldn’t resolve ms-appx://io.cordova.myappXXXX/assets/images/myImage.png because of this error: DATA_NOT_AVAILABLE.

My workflow:

1. creating ember.js app

2. folder for images:

   myEmberProject/public/assets/images/myImage.png

3. Image-HTML tag within a template:

   < img src="assets/images/myImage.png" alt="Image not available"/>

   // = ''

4. Running this app in a browser (firefox, chrome etc.) works great for me, so next step...

5. run 'ember build'

6. copy all folders/files from

   dist/

   to

   myCordovaProjekt/www/

7. Debug / Run Cordova directly to my windows phone

8. App is opening, js and css files are ok, but i get no image, only the alternative text

   Image not available

What am I doing wrong?

Thank you for helping me!